Future Ted describes the Thanksgiving of 2009, when Lily and Marshall invited the gang over to their condo for dinner. Marshall had picked out a wonderful turkey, but had left it in the cab. Robin and Ted pick it up at the Port Authority, and in gratitude, Marshall bequeathes one of his slap bet slaps to them, on the condition they slap before sundown and decide amongst themselves who gets to slap Barney.
Lily's estranged father, Mickey shows up. Divorced from Lily's mother, Mickey had been living in his parents' (Lily's grandparents) basement, trying to develop his strange board game ideas and taking advantage of his father's generosity. Marshall describes the look he saw in Lily's eyes at that moment, calling it the "you're dead to me" look. She had used the look on other people for trivial reasons, but she had not spoken to or of her father for three years.
Marshall, used to a close-knit family (he teleconferences with them for Sunday dinner), tries to convince Lily to allow her father to have dinner with them. She stubbornly refuses, but Marshall invites him in anyway, only to see Lily walk out the door. As they sit and wait for Lily to return, they play one of Mickey's unsuccessful games, "Diseases." After a part of the game sprays lead paint and horse bile all over the turkey, Marshall kicks him out and looks for Lily.
She finds him at Mr. Park's bodega, a man she had given her "you're dead to me" look. While she waited at the counter, hoping to avoid Mr. Park, she found out that he had died, which makes her depressed. Realizing what it would mean if her father died without seeing him again, they return to have Thanksgiving dinner together (inadvertently upsetting Mr. Park's widow).
Meanwhile, Ted and Robin playfully argue about who should slap Barney, begging off the honor to each other, but quickly start arguing seriously. Barney tries to extend the argument (to pass the deadline of sundown), frightened of the prospect of being tied to a chair and slapped. Eventually, Robin gifts the slap to Ted, praising his growth since being left at the altar. Ted gifts the slap to Robin, as closure to her relationship with Barney. Robin gifts the slap to Mickey as a welcome to the gang. Mickey gifts the slap to Lily as an apology for his absentee parenting. Lily can't bring herself to slap Barney, and Marshall explains that he gave out the slap to bring everyone together. A nerve-wracked Barney is released from the chair, but before he can sit down to dinner, Marshall slaps him in the face proclaiming, "That's four!".
As a postscript, a commercial is shown of Mickey's new board game, Slap Bet, recreating the gang's tradition of slaps as a family game.