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"Believe me, I know what it’s like to feel all alone … the worst kind of loneliness in the world is the isolation that comes from being misunderstood. It can make people lose their grasp on reality."
―Sienna Brooks[src]

Sienna Brooks is the hidden true main antagonist of Inferno, the fourth book of the Robert Langdon series. In the 2016 film adaptation, she is portrayed by Felicity Jones. Unlike in the book, Sienna Brooks is killed when she activated a bomb to rupture a bag containing Zobrist's virus.


Early Life[]

At the age of four, Sienna had hobbies such as violin, chess, biology, and chemistry; she also had beat a grand chess master at his own game, could read in three different languages, and was a celebrity in scientific circles. A year later, she was a child theater prodigy, starring as Puck in Shakespeare's A Midsummer Night's Dream. With her excellent memory skills, in a single night, she had memorized every character's lines and cued her fellow cast members during the first rehearsals. She grew up catholic so she most likely frequented the church as a child in spite of her never believing in God.

By the time she was seven, Sienna had displayed a 208 IQ. She was then a virtuoso violinist, could master a new language in a month and was teaching herself anatomy and physiology. With all these medical texts, she had read enough to diagnose herself with deep depression. Her parents took her to a psychiatrist, who told her to focus on the problems of the world rather than her own. This was also the age when Sienna thought she had read The Divine Comedy.

A year later, she had ran from her home in Blackheath, London to an upscale hotel; there, she had stolen a key, had pretended to be the daughter of one of the guests, and lived alone, undiscovered for ten days by ordering room service from someone else's account, and occupying herself with Gray's Anatomy to figure out what was wrong with her brain. Throughout her childhood, she had tried to attend regular schools but was frequently teased by the other kids since she didn't fit in which caused her depression. She felt isolated for her intellect was too much for her social skills to keep up; thus, she was ostracized by the other students.

Teenage Years[]

Following the psychiatrist's suggestion, Sienna started a philanthropic initiative, ladled soup to the homeless, and read books to the blind. None of the people she helped noticed that she was different as they were simply glad that someone cared, and she felt much better to the point that she was no longer depressed. Sienna worked harder every week and, although people told her to slow down for she could not save the world, she considered it a terrible thing to say and continued.

A local humanitarian group came in contact with her for a monthlong trip to the Philippines, and she jumped at the chance. When they arrived in Manila, they didn't feed poor fishermen nor farmers as she had thought, she gaped in horror at the scale of the poverty that wasn't something she had ever seen. For every person she helped, there were hundreds who were starving, and looking at her, desolated. The chaos of traffic-jam, pollution, sex trade with children made her depression return. Sienna felt suffocated so she ran away until she ended up in a shantytown where she experienced almost getting raped by three men, but she was saved by a deaf, elderly woman who stabbed one of them in the back. Sienna left the Philippines at once, not ever speaking about what had happened to her with anyone.

Instead of the incident fading away as she initially thought it would happen, she was constantly reminded of it, even months later, and felt at risk everywhere. Sienna took up martial arts, but not even after having mastered the deadly skill of dim mak she felt safe. Her depression was worse than ever, and her hair started falling due to telegenic effluvium, a stress-related alopecia that could only be cured by curing the stress, so she shaved her head and bought a blonde wig.

Her experience in the Philippines left her desperate to leave her life behind so Sienna moved to America and attended medical school, hoping it would make her feel as though she was doing something to help the world. With her intellect, school was easy for her, and she took a part-time job as an actress to win some extra money; while acting she felt as though she was someone else and not her troubled-self.

Later Life[]

For a few years, Sienna worked for the Consortium, where she was able to use everything she had learned during the time she worked as an actress, and some more. The provost's organization gained from her intelligence as well as her language skills.

Her visit to Manila sparked in her a deep concern about overcrowding and world population which led to her getting to know Bertrand Zobrist's work, a genetic engineer who had some progressive theories about the matter. Sienna became a fan, reading his writings and watching his lectures on the internet. Zobrist believed that the world could be saved, and she became obsessed with him. She studied his calculations carefully, becoming desperate that no one else seemed to notice his predictions of an imminent Malthusian catastrophe.yes

In January of 2007, Zobrist was to give a lecture in Chicago, and Sienna faced a blizzard on foot to attend. Not all his listeners had her determination, and when he arrived, the auditorium was nearly empty, so Zobrist invited the few guests to his hotel next door where they all had drinks while being lectured by him. One by one, the guests left and after the two of them were on their own, Zobrist invited her for a drink in his room, and they started a relationship. Sienna became Zobrist's love and disciple. For five years, they were both active in the transhumanist circle, a group of great minds who had indeed the ability to change the world. At that time she adopted the code name of FS-2080 in honor of Fereidoun M. Esfandiary's naming technique, which consisted of the initials of first and middle names along with the year one would turn a hundred years old.

Dr. Elizabeth Sinskey, the director-general of the World Health Organization (WHO), considered Zobrist a dangerous man for his line of thought and started following him. So in 2012, Sienna introduced him to the provost, who could help him get rid of everyone from the WHO so he could work in peace on his masterpiece. Sienna did not know that Zobrist would isolate himself from everyone in Florence, including her. He sent her a letter telling her that he would die in the forthcoming year and did not want her to see him deteriorate. She tried to contact both Zobrist and the provost for information on his case but to no avail.

Dr. Sienna Brooks

A year later, Sienna received another letter from Zobrist, this one explaining thoroughly his masterpiece: Inferno. It was a viral vector that could change human DNA so that people would become infertile; it is only active in one third of the population. She was shocked to read what he had created and went to Florence to find him so she could beg him to destroy it before the authorities had access to it. However, Sienna was too late and only found Zobrist when he was about to jump to his death from the Badia Tower while trying to escape the WHO.

The provost contacted Sienna saying that Zobrist had left a cylindrical object for the WHO (but it was only to be delivered a week after his death), Dr. Sinskey had managed to get it, and he needed help getting it back, she agreed for it was a way to know where Inferno was so she could destroy it herself. Five days later, the Consortium captured Robert Langdon who had been summoned from America to help solve the clues the cylindrical object held. The Consortium tried to get information from him, but Langdon refused to give any so he was given benzodiazepines to wipe the memory of the past two days.

Role in Inferno[]

The Consortium created the illusion that Langdon woke up in a hospital after being shot in the head. Sienna presented herself to Langdon as the doctor who would help Dr. Enrico Marconi, the Italian physician responsible for Langdon's case, since he didn't speak English very well. She examined him, gave him drugs to help him relax from the stress of not knowing what he was doing in Italy or what happened in the past 48 hours, but assured him that they had no idea what he had been through in the past couple of days; all the doctors knew was that he had stumbled into their ER with a bullet wound on the head. It was all a scheme since she was to gain his trust and stop him from contacting the WHO.

Sienna and Robert fleeing the hospital

When Vayentha, another woman working for the Consortium, entered the room and pretended to kill Dr. Marconi while on her way to kill Langdon, Sienna helped him escape to an apartment the organization had put together to pretend it was hers. Sienna left the apartment briefly to fetch clothes for Langdon, and he took the opportunity to try to know what he had done by acessing his e-mail account, which allowed the WHO to know his location and send a powerful unit to rescue him.

Noticing the agents arriving, Sienna fled with Robert Langdon and stopped contacting the Consortium since she had her own ideas of what to do once they solved everything. While dodging the WHO and the police throughout Florence, they began working on clues which led them to Palazzo Vecchio where they discovered that not only he had been there the night before with Ignazio Busoni, but also that he had stolen Dante Alighieri's death mask, which belonged to Bertrand Zobrist, a crucial item to solve another clue. They managed to escape the police once again and went to the Baptistry of San Giovanni where they met Jonathan Ferris, one more employee of the Consortium, this one pretending to be working for the WHO, but in truth hoping to get Langdon back to their side and not Sienna's.

The trio left to Venice, in the way, the provost contacted Ferris and told him that they had started working with the WHO, and Ferris informed him where they were going. Sienna tried to warn Langdon about him not being an ally, and while in St. Mark's Basilica, the two of them left Ferris behind. However, shortly after solving another clue, the WHO managed to capture Langdon, and Sienna was alone again.

The last clue sent them to Istanbul where in the Basilica Cistern was Inferno. Sienna arrived before Langdon and the WHO, but they were all too late since rather than setting the date of Inferno's release, Zobrist had set the date of when the virus would have reached most of the world population and could not be stopped. Thinking the authorities would blame her for releasing Inferno, Sienna fled, but Langdon went after her and after a long pursue, she gave up, and willingly returned to him so she could explain everything.

Sienna told Langdon about her relationship with Zobrist and the letter he had sent her about Inferno. She explained that she was afraid that if the WHO got the virus, the organization would use its technology to produce weapons so she wanted to get to it before everyone else so she could destroy it. Fearing imprisionment, Sienna was ready to leave right after she delivered the explanation, but Langdon stopped her and asked her to trust him that since she was the only one with knowledge on Inferno, the world needed her. Making a herculean effort, Sienna agreed.

Langdon took her to the Swiss Consulate where Sienna spoke to Dr. Sinskey, letting her know of everything she knew about Inferno. After hearing everything, Dr. Sinskey was sure that Sienna would be crucial at a meeting in Geneva in a few hours' time due to her different line of thought. They were going to discuss the crisis and prepare an action plan so Sienna agreed to go with her. Then, they said goodbye to Langdon as he was returning to the United States and left to Geneva.

Physical Appearance[]


Sienna was described as tall and lissome, and several times throughout the novel, it was said that she was attractive and had a slender body in general, including her hands; though she had strength enough to help a man as tall as Robert Langdon get to her apartment while sedated. She moved with “the assertive gait of an athlete” and had a willowy ellegance about her according to him. Her complexion appeared smooth, even though she was not wearing any makeup. Her eyes were a gentle brown, and the only blemish on her face was a tiny beauty mark just above her lips.

Her hair was blonde and shoulder-length, and was always tied in a thick ponytail, even in the pictures Langdon saw of her as a child in the newspapers' articles. Later on, it was revealed that it was a wig. Her baldness is related with her childhood trauma and the stress of never finding a place where she truly belonged.

According to Marta Alvarez, the only resemblance Sienna and Robert Langdon shared was their height. Sienna didn't appear to be neither older nor younger than she actually was since Langdon thought she was in her early thirties and it was said that she was thirty-two years old.

Personality and Traits[]

Sienna was quick-witted, seldom allowed herself some self-pity, could be playful, joking at several times, but she could also be completely focused on work and the task ahead of them. Her childhood passion for theater, and later on her job as a part-time actress, gave her the ability to feign emotion incredibly well which helped she and Langdon escape at quite a few times. At the hospital room the Consortium had put together, she transformed from a desperate friend and acted like a seasoned ER doctor dealing with a crisis after Dr. Marconi had pretended to be dead. When Ferris joined them, Sienna asked him directly “What's wrong with your face?” causing Langdon to remark that her bedside manner could use some work, but she replied that she was just being honest. It is possible that those two situations were just an act since she was working for the provost in the first one, but didn't want him interferring again in the latter.

Although she was playful, due to her depression, Sienna was always trying not to relapse so a general positive attitude was almost a necessity to her. When she was seven, and her depression settled in, Sienna told the psychiatrist that she wanted to be happy even if that meant not taking drugs for her condition. As a child, Sienna liked to be liked, trying to fit in and pretending to do so with her acting skills as she became older. However, she wasn't positive at all times for she believed that governments would prefer to use any technology available to make weapons rather than believing that they would use them for good, so Sienna did everything she could to prevent the authorities from having access to Inferno.


The Brookses[]

"They seemed dumbfounded, as they usually were by the strangeness of their own daughter."
―Description of the Brookses' reaction to Sienna diagnosing herself with depression[src]

It was said that Mr. and Mrs. Brooks were more often than not stupefied by what their daughter could do growing up. However, it is unknown how Sienna's relationship with her parents really was. Still, they sent her to doctors, caring for the girl's wellbeing, and the note on London Globe Theatre's playbill “Sweetheart, never forget you're a miracle,” suggests that she had at least one loving parent. They named their daughter Felicity and, judging by the articles calling her by her middle name, they didn't mind that she shunned her first name in favor of her middle one which hints that they loved her. Yet, their love was not enough to make her feel as though she belonged to the point that she ran away from home at the age of seven.

Bertrand Zobrist[]

"He was my first love. He became my mentor."
―Sienna Brooks on Bertrand Zobrist[src]

Sienna was first impressed by Bertrand Zobrist's work; the more she read, though, the more felt like she was looking into the heart of a soul mate. Despite the fear that his ideas sparked in her, she became obsessed with him. For years, she read his articles and watched videos of him until the day came of when he would give a presentation in the USA. Sienna knew that nothing would stop her and faced a blizzard in Chicago to meet him.

Although there were 500 tickets sold, only a dozen guests attended the lecture. Zobrist called the guests to his hotel and they all had drinks while hearing his tales, but one by one, they left. By midnight, Sienna was the last one, complimenting him which Zobrist took as flattery, flirting with her. Later that night, she lost her virginity to him, and they started a long-term, loving relationship.

Zobrist was her lover as much as he was her mentor. He taught her all about transhumanism and introduced her to the circle of people that would made her feel part of something from the first time in her life. They lived happily for five years until Zobrist isolated himself from her without warning so he could work on Inferno. After a year, when Sienna learned of what he had done, she became desperate; she tried to find him so she could beg him to destroy his creation, but she only found him in time to see him look into her eyes from the Badia Tower before committing suicide.

By the end of the book, Sienna told Langdon that she met Zobrist at an impressionable age, that both his ideas and intellect bewitched her; she also told him, but this time along with Dr. Elizabeth Sinskey, that she believed Bertrand Zobrist's actions were reckless and extremely dangerous, and that she would have stopped him in a heartbeat if she could.

Robert Langdon[]

Robert and Sienna in Venice

"She found herself strangely attracted to the American professor. In addition to his being handsome, he seemed to possess a sincerely good heart. In some distant, alternate life, Robert Langdon might even be someone she could be with."
―Sienna's thoughts on Robert Langdon[src]

From the beginning of the novel, Sienna thought of Langdon as someone she could be romantically involved with since her previous boyfriend had just commited suicide. However, she still carried on the Consortium's plan and lied to him about her identity for three-quarters of the book, though later on she mentioned that she had no choice.

In between, in spite of the seriousness of the situation they found themselves in, they had a rather playful relationship, pretending to be siblings at several times; joking and rolling eyes at each other, including about Dante Alighieri's death mask when Langdon pretended to be baptizing the poet while whipping the mask in his baptismal font. They developed the habit of asking each other the question “A penny for your thoughts?” but changing the word penny for the currency of the country they found themselves in.

From the moment they got separated, Sienna felt incredibly lonely and missed Robert by her side; a few chapters later, it was stated that the feeling was mutual despite his distrust to her at that point of the story.

Sienna: "Robert, I … I don’t know what to do. I don’t even know who I am anymore. Look at me. I’ve turned into a monster. How can I possibly face—"
Robert: "Sienna, I know you want to run, but I’m not going to let you. Sooner or later you need to start trusting someone."
Sienna: "I can’t … I’m not sure I know how."
Robert: "You start small. You take that first tiny step. You trust me."
— Sienna Brooks and Robert Langdon[src]

It was said that Sienna had trouble trusting people, especially regarding weapons and how governments can use any technology available to create them. Still, Langdon was the only one who she could trust to take any kind of action that would allow her to help those agencies. At his request, she agreed to talk with the WHO and tell them everything she had read in Zobrist's letter to aid in the crisis that would follow. Dr. Sinskey then asked her to attend the meeting in Geneva, so Sienna and Langdon parted ways.

While saying goodbye to Robert Langdon at a private terminal, she told him that she wished he was coming with them and asked if Robert thought that he was too old for her, showing that she was in love with him. Langdon said that he thought that he was definitely too old for her, but also said that he would like to see her again. Still, Sienna kissed him on the lips and told him that she would miss him, Robert replied that he would also miss her, then told her of an ancient saying often attributed to Dante Alighieri: “Remember tonight for it's the beginning of forever,” and that it was her chance to save the world. While getting on the plane, Sienna prayed that Dante was right.

Dr. Elizabeth Sinskey[]

"I suspect Sienna Brooks and I will find plenty of things to learn from each other."
―Dr. Sinskey[src]

Being someone with issues to trust people, Sienna thought that the director-general of the World Health Organization was not someone she should trust. She feared that Dr. Sinskey would help government agencies turn the viral vector Zobrist had created into some sort of weapon so she went great lengths to prevent the WHO from finding it. Dr. Elizabeth Sinskey also did not trust her for everything she had done, thinking Sienna was working with Zobrist to release the plague. However, as it was proven impossible to stop Inferno, Langdon convinced Sienna and Dr. Sinskey to work with each other at the end of the novel, with the younger doctor telling the older one everything she knew about Inferno and how the knowledge could help the WHO. Sienna's line of thought was nothing like the WHO's and at that time of crisis, it would be needed in Geneva to explain the situation and Zobrist's actions. Later on, it was said that being from different generations and thinkings, they could teach each other quite a lot.


  • Felicity has Latin origins and it means “good fortune, happy.”
    • As Sienna considered herself neither fortunate nor happy, she shunned her first name as a child, possibly as soon as she learned the meaning of the word. The abandonment of her first name was an attempt to escape her identity, which had been happening since she learned to speak.
  • Sienna refers to the orange-red color clay produced by the homonym Italian city.
    • In Dante's days, the Tuscan city of Siena (with one “n”) was a Ghibelline stronghold, a frequent rival of the poet's Guelph-held beloved Florence in bloody conflicts. Many times during The Divine Comedy, Dante comments that Siena's government does things better than Florence's, but the latter tended to look down on it for Siena was almost insignificant. However, Dante also says that Florence was infested with not only political but also moral corruption.
    • Much like The Divine Comedy, Sienna's story throughout the book is of treachery and that was what Dan Brown was aiming with choosing such name for his co-protagonist. Dante was two-sided toward the city Siena and the character turns out to be a double agent, even if it is only stated near the end of the novel, the ambiguity of the character is present.
  • Her surname Brooks may refer to the several rivers Dante took from the Greek mythology and reworked as landscape in his Inferno in which Cocytus, a Greek mythology river in the Hades, is frozen and the home for the traitors. The Lethe, another river Dante borrowed from the Greek mythology, causes amnesia at the end of his Purgatorio once he bathes in its water. Beatrice then chides Dante for his amnesia and not realizing his sins which can be seen as a clear analogy to Sienna showing Langdon that despite his amnesia and the supposedly sins he committed in trying to stop Zobrist's virus, her intentions were good in the end.