As with her Swedish counterpart, Elise is noted for demonstrating traits consistent with Asperger syndrome, such as difficulty in understanding or recognising social concepts such as empathy, sarcasm, and lying; also, she possesses an above-average intellect, a good eye for detail and a reputation for thoroughness.
However, there are some differences between the two characters' personalities; Elise is less guarded about her emotions and has less difficulty in forming social relationships (including some romantic ones).
[3] As she spends more time with her British colleague, Karl Roebuck (Dillane), he coaches her through social scenarios where she normally struggles, and makes more allowances for her when she messes up.
Critics generally praised both Poésy and Dillane's chemistry, with Rebecca Smith of The Daily Telegraph comparing their relationship to that of the protagonists of Broadchurch,[4] and James Stansfield of Den of Geek observing that it created a "powerful" finale.
Later in the series, and to her own surprise, Elise develops feelings for Eryka Klein, a German woman who worked alongside a French judge killed in the aeroplane crash she was investigating.
In "Episode 2" of Series 3, Elise tells Maya Roebuck that she lost her virginity to a boy when she was thirteen years old, and to a girl when she was fifteen.
Their relationship gets off to a frosty start when Elise ignores all social niceties and rudely tells Karl that the operation falls under French jurisdiction (before they discover the second body).
As the investigation begins, Elise's eye for detail quickly helps to identify the slaughterhouse where the victims were dismembered, and clear the fascist farmer who owned it as a suspect, when she realises that he doesn't understand English.
However, her lack of social skills and bluntness quickly get on Karl's nerves, particularly when she makes an insensitive comment to an elderly woman that they are interviewing when the second "truth" occurs.
In turn, she comes to find his sarcasm and willingness to bend procedure to be obstructive, when he allows another suspect, Charlotte Joubert, to leave when Elise was about to interview her.
However, it takes a severe knock when Karl discovers that his teenage son, Adam, spent the night at Elise's apartment, and is only barely reassured when she explains that she did not actually engage in physical intimacy with him.
In addition, it is shown that, despite her outwardly unemotional demeanour, Elise continues to be haunted by the death of her twin sister, whose photograph she keeps on her desk.
When Karl notices the effect that it has had on her, Elise reveals that her sister had drowned when the two had been dragged out to sea by a riptide when her parents had taken them on a beach holiday, and that they had only managed to rescue her.
When a potential lead points to a former French policeman, Fabien Vincent, as TT, Elise organises an ambush to try and take him into custody, but it proves a failure, much to her anger.
While he searches for his son alone, Elise has an idea; she tracks Fabien Vincent down and gets details on a property that the organisation that he and Ashton had worked for, Peloton, had used as a safe house.
While attending a management class (which she takes to improve her leadership skills), she is called to the Folkestone to interview Chloe Fournier, a little girl whose mother, Madeleine and stepfather, Robert, were kidnapped in the Channel Tunnel.
Unbeknownst to the group, Robert Fournier, an ideological anarchist, had actually staged the kidnapping, and after executing Madeleine, leads his team in a major act of terrorism: with the help of some inside agents and his deceased wife's research, he hacks into the autopilot of a passenger plane and crashes it into the Channel, killing all on board.
She had been born and raised on the notorious Colonia Dignidad colony in Chile, where she had been subjected to sexual assault, and had lost her twin brother early in her life.
Elise is prevented from pursuing him when she sees the body of a woman he killed floating in the water, and freezes as the image causes her to have flashbacks to the day her sister died.
The aircraft crash was a mere demonstration, and Baturin has a nuclear option to ensure he is not arrested - Edgar Branco, a psychopathic doctor from Colonia Dignidad who possesses a variety of dangerous viruses capable of infecting thousands.
Suspicion soon falls upon Eryka, who didn't board the plane due to a supposedly lost passport and had a close relationship with Bresson and his timetable.
Realising her cover has been blown, Eryka confesses to her involvement, explaining that she sides with Baturin because the United States had been fully aware of the goings on in Colonia Dignidad.
After Gregor dies unexpectedly of a heart attack, and their attempt to apprehend Artem fails, Karl is contacted by the MI5 officer investigating him, Neil Gray.
At that moment, the police storm the building; out of love for Elise, Eryka had covertly phoned her handlers in Russia and persuaded them to broker a new deal with Neil.
The unconscious Elise is rushed to hospital, while Karl and Olivier arrest Baturin, and Neil ushers Eryka onto the helicopter, having agreed to allow her to walk free as part of the new deal.