To begin his day, Jasper Tempest washes his hands thoroughly, then immediately puts on latex gloves. He arrives precisely on time to teach his class in forensic criminology at Cambridge, his desk having been wiped down by his assistant. He uses hand sanitizer on his gloves and begins.
A man rushes in, shoves him over, and steals his briefcase.
The lesson is on perpetrator identification, Professor T explains as he dusts himself off. Even though the entire class saw the crime happen, almost everyone fails to describe the perpetrator accurately. Trauma scrambles the memory, Professor T lectures, as the brain tries to protect us from the shock. His disdain for his students’ failure is clear—so clear that the dean later chastises him. Tenure can be removed, the dean says carefully.
At least one former student has gone on to apply Professor T’s teachings, however. Lisa Donckers is a detective. While investigating the rape of a young woman, Diana, in a dorm bathroom at Cambridge, she decides to ask Professor T for help. There is no forensic evidence, given that the bathroom is well-used, and the woman is traumatized and can’t remember much detail about the attack. Lisa wants Professor T to help unlock the woman’s memories.
Lisa suspects this is a serial rapist. Five years ago, while she was a student, her friend Saskia was raped when she left a party early without Lisa. The attacker took Saskia’s necklace; Diana also had her necklace ripped off. Plus, there were similar carvings at both attack scenes. Saskia has avoided Lisa ever since.
But Professor T’s interest in crime is purely academic, he tells Lisa, refusing to help.
Nevertheless, Lisa brings Diana to Professor T. Diana wants to help in apprehending her attacker, but begins to shy away as Professor T tries to talk her through her memories. She’s not ready, he says, and leaves.
Lisa’s contacts with Professor T have been unsanctioned, and she has asked her partner Dan—with whom she recently slept after a drunken night out together—to cover for her. But their boss, Christina, easily gets the truth out of Dan. She knows Professor T, and tells Lisa it’s a good initiative. Christina texts Professor T, asking him to come in the next morning. The last text she sent him was from 2009: “I never want to speak to you again.”
Professor T arrives at the police station and lectures on the typical profile of sex offenders. Dan and Lisa’s supervisor Paul Rabbit goes through their suspects: men who have access to the campus buildings and prior charges. Henry Watson works in the canteen and has a charge for indecent exposure. He ran and escaped when Dan and Rabbit tried to speak with him. Dennis Banks served time in prison and now cleans the college, but his wife vouched for his whereabouts the night of Diana’s rape. Lastly, there’s a caretaker who has a decade-old drunk driving charge. Since the previous rape was five years ago, the police are not investigating students.
Professor T recognizes the carvings at each attack as Bible verses about unclean women. Given that the attacker hasn’t struck for five years, Professor T fears that he has lost control and will soon commit more crimes.
Indeed, a student named Milly is attacked that evening. She manages to pepper spray the rapist after he grabs her necklace off her, then flees before falling down a staircase and hitting her head. She’s now in a coma. The police only identify her as another victim when they visit the hospital in search of other women who may have been attacked and smell the pepper spray on her clothes.
Dan is keen to go out with Lisa again, but she resists—not that she doesn’t enjoy his attentions. He’s not the only one dreaming of romance: Professor T daydreams about dancing with Christina while he sits in his customary spot on the roof of the college, looking out over Cambridge. His mother, Adelaide, interrupts his reverie.
She has put his childhood home up for sale—it’s madness to sit on a gold mine when you can’t set foot in the place, she says—without telling Professor T. He, of course, found out, and cancelled the sale. He’s going to move in, despite his mother’s protestations that it’s a “shell of unhappy memories.”
Diana is ready to revisit her own traumatic memory—she doesn’t want more people to be hurt. Rabbit tries to interrupt Professor T and Lisa’s meeting with her, but Professor T tells Rabbit to deal with his obvious personal problems and let them solve the crime. Lisa tells Professor T that Rabbit lost his only daughter six months ago in a hit and run. But when Christina asks how he’s doing, he would rather not talk about it.
Professor T guides Diana through her trauam as an outside observer, so that she can overcome her mental barriers. The exercise leads her to cry but also reveals a new detail: the assailant had a tattoo with five dots on his hand. It’s a common prison tattoo.
The police arrest Banks. He has the tattoo, is religious, and has Diana’s necklace, which he claims to have found while cleaning. The only problem is that his wife swears he was at home sleeping during the attack.
Professor T and Lisa interrogate Banks, prying into psychological weak spots before asking him when he found out his wife was having an affair. He opens up. He pretended to take a sleeping pill because his wife was acting funny, then heard her talking on the phone and leave for a date. Perhaps that revelation led him to rape again, Professor T suggests.
Dan enters with a note for Professor T. Milly is out of her coma, Professor T tells Banks. Lisa asks for an admission of guilt. Banks gives it.
Lisa looks at Dan’s note after Banks is taken away. Milly has died, it says.
Back at his university office, Professor T receives a thank you note and a fishbowl from Diana: she stepped out of the fishbowl protecting her mind, as Professor T described it.
Rabbit drinks alone at work.
Lisa visits Saskia: we got him, she tells her.
And Professor T moves into his old home, where, as a child, he found someone—his father?—hanging from a noose.