This is the third and final episode of the first series of channel 4's Black Mirror. It was first broadcast on the 18 December 2011.
Set in a reality where most people have a 'grain' implant which records everything they do, see or hear. This allows memories to be played back either in front of the person's eyes or on a screen, a process known as a 're-do'.
Liam Foxwell (Toby Kebbell), a young lawyer, attends a work appraisal which he feels did not go well. After leaving the meeting he replays his memory of it and dwells on a seemingly insincere phrase used by his employer. He arrives at a dinner party hosted by some of his wife's friends, and sees his wife Ffion (Jodie Whittaker) talking to a man he doesn't recognise, whom she introduces as Jonas (Tom Cullen). Some of Ffion's friends ask how the appraisal went and suggest replaying it as a 're-do' so they can all give their opinions on it, but Jonas steps in to save Liam from the embarrassment.
At dinner, Jonas speaks increasingly frankly about his personal life, and talks about masturbating to re-dos of sex from his earlier relationships. Throughout the meal, Liam becomes suspicious of how fondly Ffion seems to be looking at Jonas, and he is especially suspicious when she laughs at Jonas's bad joke.
When Liam and Ffion return home, it transpires that Ffion had had a previous relationship with Jonas many years ago which she had mentioned to Liam but downplayed. She initially said it lasted a week, then says a month, and then admits it was six months. These initial lies make Liam even more paranoid and he insists on replaying footage from the evening and demanding explanations for why Ffion said and did the things she did. Ffion becomes increasingly uncomfortable with his relentless questioning and the conversation turns into a row. Liam apologises and they have sex, but they are both watching re-dos of more passionate sex from earlier in their relationship. After they finish, Liam goes back downstairs and watches re-dos of Jonas' frank confessions from the dinner party, whilst drinking excessively. He continues this all night, and the next morning argues with Ffion about her laughing at Jonas' joke. She goes back to bed and he drunkenly drives to Jonas' house, where he confronts him about his relationship with Ffion, and threatens to cut Jonas' grain out of his neck if he doesn't delete all the footage of her stored on it. Jonas complies, and Liam drives away, crashes his car into a tree and passes out.
When he wakes up, he replays his latest memories with increasing horror, and walks home to confront Ffion - as Jonas projected his footage of Ffion onto the wall screen before deleting it, Liam noticed that there was a file proving Jonas and Ffion last had sex eighteen months ago, around the time their daughter Jodie was conceived. Ffion admits to cheating on Liam, saying that it was when Liam had temporarily walked out after a row, but insists that she and Jonas did use a condom and that Liam is the baby's father. Liam demands that she replay the re-do of it to prove it. She tries to erase the memory but he stops her, and she plays the footage whilst sobbing and unable to look at the screen. It is unclear whether the video proves or disproves Liam's suspicions, although it is heavily hinted that they were correct.
Liam is shown wandering through the house, which is now untidy and half-empty, and Ffion and Jodie are gone. Happy memories of his wife and daughter appear as he walks through each room, until, tormented by these re-dos, he messily cuts his grain out of his neck with a razor.