Eve’s husband Niko is strong, moral and appreciates the simple things in life. He was born in England to Polish immigrant parents and grew up on the wrong side of the tracks. He has an aversion to violence, and can’t understand Eve’s fascination with darkness and criminality. He’s smart, wildly compassionate and though he perhaps can’t admit it to himself, prefers his wife in a boring desk job than in close proximity to danger.
Deep down he knows there is something darker living in Eve. He dislikes her flippant humor towards violence, her fascination with assassins, how impressed she is with them, and her “how would you kill me and how would you dispose of my body” conversation topics don’t do it for him — but he never thought she’d slip too far down the slope…
Niko and Eve moved from a practical, loving and close couple to two people heading for separation. They used to speak regularly and tell each other everything. Eve stops communicating and worse, she starts lying. Once the reliable, sympathetic husband, now Niko starts rethinking their relationship. And he wonders if Eve is the person he thought she was.
In London, Eve Polastri screams in her sleep. Her husband, Niko, wakes her up and Eve tells him it was because she fell asleep on both arms. She has a headache from staying out late the night before and singing karaoke with her co-workers for her boss, Bill's, birthday. Even though it is Saturday, she has to go into work at MI5.
Eve visits Niko at his Polish bridge club and recruits him and a Polish teenager, Dom, to listen to the recording of Kasia's babbling about the assassination. They decipher that Kasia is using slang and the assassin was tall, dark, and flat-chested, a "small-breasted psycho."
Eve is impressed with the murder of Kedrin from a tiny puncture wound and asks Niko how he might kill her. Niko says he might push her down the stairs or flatter her to death. She tells Niko she would paralyze him with saxitoxin and suffocate him in his sleep, chop him up, boil him down, put him in a blender, and then flush him down a restaurant toilet. Later, as they're going to bed, Eve questions whether or not the CCTV recording is real. Niko tells her she should have been a spy.
Eve is at home watching television with Niko when her doorbell rings. Carolyn invites her to walk to the corner shop where she reveals to Eve that Villanelle has been operating for two years across ten countries.
Niko cleans off a freshly laid egg from a chicken in their house as Eve wonders whether it is edible. Niko questions her about her new job and Eve explains it is just gathering and analyzing information.
Niko arrives home early as Eve struggles to get a suitcase down to begin packing for her trip to Berlin. He reminds her to label her suitcase so that she does not lose another one.
Bill apologizes to Eve for losing her suitcase as they scope out Jin's location. She mentions that Niko will be upset about her losing the green scarf. Back at the hotel, Niko video calls Eve from a dinner party at their house that she had forgotten about. Niko asks her about her new dress and she explains about the dinner with Jin.
Eve and Niko attend Bill's funeral service, seated behind Bill's wife, Keiko, and their baby daughter. Frank goes up to say a few words and Eve is disgusted with his terrible speech. When Bill's daughter begins crying, Eve stands up and hurriedly leaves the service while Frank is still talking.
Niko offers Eve stew and wine while Eve sits forlornly on the couch. Niko confronts Eve about Bill's death and how he is worried about her. They briefly fight before Niko informs her that her suitcase has returned from Berlin.
Eve is sitting on the edge of her bed and crying. She gets her suitcase and opens it, discovering it has been repacked with new clothing with the tags still on. She finds a box of "La Villanelle" eau de parfum. The card inside reads "SORRY BABY x." Eve hastily tosses it back into the suitcase and warns Niko to stay out.
Eve sits at a bus stop and pokes at a crack in the windscreen. She stands up and slams her fist against it, shattering the window. Her phone rings and she answers Niko's call, telling him to bring Dom with him. She hurries away from the bus shelter.
Villanelle is with Eve at Eve's house when the door opens and Niko and Dom enter. Eve begs for their lives as Villanelle picks up Eve's phone and asks for her PIN ("1234"). Villanelle takes Eve's phone and dress and says hello and goodbye to Niko and Dom on her way out the door.
Eve rushes over to Carolyn's house where Carolyn takes her and Kenny into another room. Eve explains that Villanelle has her phone, which gives her access to Frank's interview and his location. She also asks for protection for Niko.
Eve meets Niko at his bridge hall and catches him smoking. He shows her a newspaper with Frank's murder on the front page, pointing out that he was at Bill's funeral and wants to know how many more people have to die. They get in a screaming match and Eve slaps and shoves him. Niko walks away before stopping and telling her they should forget about the fight and get some dinner. Eve tells him she can't; she has to got to Moscow.
When Eve arrives at the hotel in Moscow, Eve calls Niko and gets his voicemail. She hangs up without leaving a message.
Niko comes home to find Eve chopping vegetables for a roast chicken she’s forgotten to put in the oven
Back in his house Eve tells Niko about how she got her job, because he understands how much Eve’s work means to her. And he knows she’ll keep doing it; all he asks is that she tell him what’s going on. She starts by confessing… that she ordered a ton of new and extremely expensive windows for their home.
Niko comes home to give things with Eve one last shot, even playing into her fantasy of fear and danger — only to feel like shit on the other side. The next morning, after a night of what sounds like very kinky sex, Eve is elated while Niko decides he's had enough. It's not about the sex, but the fact that Eve never told him she stabbed Villanelle. He realises that he will never be the person she really wants, and he leaves, despite her protests.
Eve attempts to make contact with Niko, who is staying at his coworker Gemma's house while they figure out their marriage. Eve has brought him some of his belongings, but when Gemma invites her in, things shortly go off the rails. In pursuit of the bathroom, Eve takes a turn into Gemma's bedroom, where she breaks her music box and messes up her clothing drawer, prompting both her and Niko to come into the room.
Even though Niko says Gemma is just a friend and he's staying on the sofa bed, Eve won't apologise, and tells Gemma, "I hope you like the missionary position" on her way out of the room.
However, keeping Villanelle under control is already proving difficult. As Niko and Gemma move his things into a storage unit, the assassin pops up with an urgent question: What is his Shepherd's pie recipe? Niko shakingly gives the ingredients while Villanelle's knife is pressed to his throat, and even though she's pleased to know the missing ingredient has been "Worcester sauce," she's not done with the pair. She sits them down on the couch and asks Niko if he loves Gemma, which he denies. He loves Eve, he says. However, that was the wrong answer.
In the final shot, Niko wakes up in the storage unit to the horrific site of Gemma bound and suffocated in front of him.