Plot

A man collapses lifeless on a bus. Covered in blood, the corpse bears no wounds; death may have been caused by a highly contagious disease.

We are on a bus in Paris; a male passenger is vaping and another passenger asks him to desist. The man stands up and collapses. Someone shouts, "Stop the bus". Raphaëlle is a mid-level police detective in Paris. She has just been called about the incident and is going to the scene. Nico, a colleague, says he will go with her, but she says don't bother, she will take Astrid. Astrid is on the autistic spectrum, and the two women have developed a bond of friendship, although Astrid needs considerable help in social situations. She works in the Criminal records Office but has often discovered clues and connections connected with crimes, unnoticed by what she describes as neuro-typical people. Nico is offended that Raphaëlle considers Astrid (a civilian) more useful than himself. Raphaëlle is unsympathetic to his feelings. She goes to pick up Astrid at her home. Astrid launches into a complicated explanation why she does not invite Raphaëlle, as a visitor, into her home. Raphaëlle hardly expected that, as she was simply giving Astrid a lift to the crime scene, but Astrid nevertheless explains that her home is kept neat and orderly, by contrast to Raphaëlle's rather slovenly lifestyle. Raphaëlle takes the rebuke on the chin and smiles. They get to the scene. The bus has been cordoned off. The man is dead, and has no identification of any kind on him. Incredibly the bus passengers are still, 30 minutes or more after the incident, sitting in their seats passively, apparently not having been told what is going on. Fournier, the police pathologist, tells Astrid, "I'm sick of all this twisted stuff; I like a stabbing or a nice strangulation." The passengers are still seated adjacent and do not appear to freak out when he goes on to detail the cause of death. No wounds or haemorrhaging. Just a mediastinal lymphadenopathy. Astrid knows about this. He must have suffered horribly for several days ... unless the symptoms struck suddenly. Fournier looks alarmed and rushes to the bus driver, still apparently at the controls, and tells him to shut the doors of the bus. It's probably anthrax poisoning, an acute and virulent infection. At this late stage a passenger on the bus asks what is going on. Astrid explains it's a possible anthrax infection, and that the bus is quarantined, but nowadays only about 50% of people affected die. But no-one else on the bus was affected, so it must have been the vaping device. It is sped to the lab and they quickly identify that it is a non-infectious strain. The bus and its passengers may be released from quarantine. The lab report indicates that the concentration is far higher than would normally be found; it must have come from a laboratory. Back at the police HQ Nico apologises for his resentment this morning. He and Raphaëlle are loosely romantically attached, and they agree to have dinner at her place tonight. We now go to an unexplained flashback; Raphaëlle is wearing a hoody to show us that it is a younger version of her; Nico is there looking older. They make small talk; they both seem to be there to apply for jobs in the police. Back in the present day, Raphaëlle, Nico and Arthur are researching where the mystery man came from. Arthur has managed to recover something from his phone. No messages, but a video clip of animals being slaughtered in an abattoir - perhaps maltreated. They can identify the abattoir, apparently, and Raphaëlle goes there to interview the boss - maybe he objected to people poking around. In fact the interview takes place at police HQ. Raphaëlle shows him the video but he says he has never seen it before, and it doesn't bother him particularly; he complies with all the laws and rules relating to animal welfare. She shows him a photograph of the deceased man, and he identifies him at once as Victor Hautin. He worked there for about ten days; if Raphaëlle wishes, he will pass copies of the information they had on him when they took him into employment. She sends him away. Raphaëlle goes to see Mme. Hautin, and tells her that her husband is dead. But in fact a man is coming from the stairway to the flats, and hears this and says he is Victor Hautin. Raphaëlle goes to see Astrid at the Criminal Records Office where she works; Victor Hautin reported his passport missing a month ago. Back at police HQ, the video of the abattoir is online, posted by an extreme animal rights group. They don't have an organised structure, but there is someone who is their leader - Cassandre Germain. There is a photograph on line; she is in prison. She had been preparing for an attack and was found with the bacillus used in the attack on the bus. Raphaëlle goes to see her in the prison, but the woman dos not offer any information whatsoever. Raphaëlle goes to see Astrid; she has been investigating the Bordeaux attack, which had similar characteristics. A man called Maxime Bermont. After the attack he disappeared and has never been found; but a bus pass in his name was found on the bus on which the dead man was found. Maxime Bermont was on the bus and Astrid has found the address used to obtain the pass. Raphaëlle goes to the address and a woman named Alexandra Germain answers the door. Cassandre Germain is her sister. Maxime Bermont is her husband. They go indoors and the woman confirms that Raphaëlle's photograph of the bus victim is Maxime Bermont. The woman has had no contact with Cassandre for a long time, but when she went to prison she took in Cassandre's child, Martin - her nephew. Was Maxime involved with the animal rights group? Well, he moved in with Alexandra and they became close; it was natural as the child lived there. But a few weeks ago Maxime said he didn't want the child to end up as an orphan like himself, and that he wanted to stop what he was doing. He was evidently thinking of moving to Costa Rica. Raphaëlle is explaining her theory - that Maxime was in the terrorist group but was planning to leave it and go to Costa Rica. The Commissioner is dubious whether there is any evidence of this, when Arthur and the infectious diseases man who was at the bus at the scene of the death, arrive. The have information from the laboratory. The strain of anthrax used on the bus matches the strain that Cassandre Germain had in her possession at the time of her arrest. The Commissioner tells Raphaëlle to go and see Cassandre and see if she can get more information out of her, and Arthur is to find out if any of the animal rights people might have been asked to eliminate Maxime Germain. The infectious diseases man winks at Astrid in a friendly conspiratorial way. As they leave Astrid gives him some eye disinfectant drops, imagining instead that he has dust in his eye. Raphaëlle goes to see Cassandre again in prison. She tells her that she has seen Martin, and asks her if she knew that Martin planned to go to Costa Rica. But Cassandre offers no information of any kind. Arthur is looking through people who may be connected to the animal rights group on the computer, and Raphaëlle is sitting with him. As they flick through profiles, they see the man who died on the bus: his name is Fringe Simon. Now Raphaëlle is questioning Martin. Didn't Cassandre order him to kill Maxime? No, he was killed right under my nose when I was supposed to protect him, on Cassandre's orders. Raphaëlle goes to see the Commissioner, but a woman named Daphnée Simoni is with him. She is with the Ministry of the Interior, and the terrorist act with the anthrax comes under their jurisdiction; she is taking the case over, and the Commissioner supports her. Raphaëlle decides to continue her investigations anyway, and has obtained an authorisation to examine relevant files at the Criminal Records Office where Astrid works. Astrid goes to fetch them bu they are missing from their place in the system. Astrid filed them away there last night and now they are missing. They must have been moved to room 438, a highly secret section of the records system, to which Astrid doesn't have access. Raphaëlle is very unhappy with this and intercepts Daphnée Simoni in the carp ark of her offices. She gets nowhere and maybe intended to assault her, but a text from Astrid distracted her. She goes now to Astrid. Astrid now knows all about the murder. It was staring us in the face. The murdered man on the bus was Louis Valméras. Everyone thought Maxime Bermont, but the stranger on the bus was Louis Valméras living under the identity of Maxime Bermont.

Raphaëlle goes back to see Cassandre. For no apparent reason she asks the prison guard to leave them alone. She tells Cassandre that she knows that the mystery man was Louis Valméras. Why protect someone who was planning to go away from you? But Cassandre grabs Raphaëlle and she has a knife. Louis and Cassandre were planning to go away together. He changed his identity to Maxime to escape the police. Inexplicably the prison guard has let them out of the interview area, and Cassandre has the knife at Raphaëlle's throat. But (she says) Louis was an undercover policeman. Cassandre slightly cuts Raphaëlle's throat but is shot dead by a prison guard. Outside Raphaëlle is all right but the Commissioner turns up and suspends her from duty. Astrid goes early to the support group for people affected by autism. William, the leader, is putting out chairs. She tells him that she thinks someone is courting her - she shows him a text. He agrees, and gives her a book on the subject of romantic relationships. She thanks him and leaves. Raphaëlle goes to see her Father. He is an important senior official at the Ministry. He is in a meeting, and they are not on good terms, but he closes the meeting abruptly to speak to his daughter. We see a flashback to when she was celebrating passing the police entrance exam; her Father was hostile to the fact that she wanted to fight crime on the ground, when she had the ability to work at the top - in politics. There is clear hostility in the encounter today, but evidently he agrees to help her. She wants access to room 438 and the secret files. She goes there with Astrid, and immediately find the files. Back at police HQ they are looking up the people involved in the Bordeaux attack, which they believe was perpetrated by the same people as the current bus attack. The Commissioner strides in and demands to know what she is doing. He was a captain in the special unit headed by Daphnée Simoni. She is able to tell him that the victim on the bus was Victor Hautin aka Anthony Valméras aka Maxime Bermont, but he was actually Paul Simoni. Married to his superior Daphnée Simoni. The strain of anthrax bacillus is not the same as the one being illegally manufactured by the EDS terrorist group, but it is identical to what was retained by Simoni's group after the Bordeaux attack. The Commissioner is persuaded by Raphaëlle's account, and gives her back her badge and gun. Now Raphaëlle is interviewing Daphnée Simoni. She had thought that Bermont had died at the Bordeaux attack, but then when they were carrying out surveillance of the EDS group, she recognised him in a photo. His betrayal of Simoni was that he had always refused to have children with her (as she had hoped for) on the grounds that their work was too dangerous; but in the photo she saw him with Cassandre's child on his knee. Back in the police office, Mr Frédéric has come in to see Astrid. He is the pathology investigator from the bus incident, who was attracted to Astrid in the first place and had sent the text that William explained. Astrid tells Frédéric that she has no feelings for him, and her customary bluntness deflates the poor man considerably. Raphaëlle walks back with Astrid to Astrid's flat. Astrid is explaining that she thinks M. Frédéric had romantic feelings for her, (feelings that are not strictly professional), but that she turned him down, being carefully not to crush him in doing so. Has Astrid ever had such feelings for anyone herself, asks Raphaëlle. Astrid doesn't know, but invites Raphaëlle in to her flat for a cup of tea, the first time Raphaëlle has been let in. Raphaëlle smiles, and we the audience are encouraged to wonder if there a feelings that are not strictly professional in play here.