Mia Nolan (Andrea Riseborough) is the main protagonist and villainess of "Crocodile", episode 4.03 of Black Mirror (airdate December 29, 2017).
As a teenager, Mia and her boyfriend Rob were driving back from a party, with Rob driving the car drunk. As they were driving by the coast, Mia was horrified when Rob accidentally struck and killed a cyclist. Afterwards, though, Mia (reluctantly) helps Rob cover up his actions by helping him toss the man and his bike into the ocean.
Events EditFifteen years later, Mia was shown to be a successful and respected architect with a husband and 9-year-old son. After giving a speech at an architect's conference, Mia was visited in her hotel room by Rob, who was feeling remorseful for his actions after reading a news article about the widow of the man he'd hit (who believed he was still alive) and revealed to Mia that he wanted to make amends by sending an anonymous letter to her confessing to what he'd done. Mia, however, objected to the idea, believing the letter could be traced back to them. An argument ensued between the ex-lovers, with Mia lambasting Rob for having dragged her into his crime.
When Rob prepared to leave the room, Mia feigned understanding and hugged him before shoving Rob to the ground and pressing her arm against his throat, killing him and establishing Mia's heel turn. Afterwards, Mia used a hotel food cart to sneak Rob's body out of the hotel and dispose of him at a construction site, buying a pornographic film to serve as her alibi and washing her car after returning home. It was soon after, however, that Mia was visited by insurance agent Shazia Akhand, who was investigating a man who was supposedly struck by a pizza truck on the night of Rob's murder (with Mia having witnessed the incident from her hotel window). In order to see what Mia witnessed, Shazia hooked her up to a device called "The Recaller", which allows Shazia to see Mia's memories of the fifteen-year-old accident and of murdering Rob despite Mia's attempts to suppress them.
As Shazia hurriedly tried to leave, Mia came to realize she had uncovered her secrets and followed her out, claiming that she had "mad thoughts" to cover for her deeds before breaking Shazia's car window and kidnapping her, tying her up in a remote shack. After ungagging Shazia, Mia interrogated her, disbelieving her claims that she would stay quiet about what she'd learned about her and that it was illegal for her to reveal anything she saw via The Recaller. After using the device to see that Shazia had told her husband, Anan, she was going to talk with Mia, the villainess beat Shazia to death with a log before going to Shazia's house and beating Anan to death with a hammer, along with their infant son (not realizing the child was blind and thus his memories couldn't be used against her).
After committing her murders, Mia attended her son's school play, Bugsy Malone, with her husband, barely able to contain her emotional turmoil from her heinous actions. Meanwhile, at Shazia's house, the investigating police used the Recaller technology on the only surviving witness to Mia's actions: the pet gerbil that Shazia's husband had recently bought. The episode ended with Mia tearfully applauding the play as the police entered the school preparing to arrest Mia.