Lily goes to Minnesota to bring Marshall back, but he's not ready to leave yet. Meanwhile, Ted and Zoey's relationship gets off to a rocky start, and Barney searches for a female "victim" the night before Valentine's Day.

The Captain asks Ted to help find out who stole Zoey away from him, Marshall withholds sex until he does something to help the environment, and Barney is reluctant to admit that he has a crush on Robin's friend.

The gang gets mad at Barney when he lies to Nora and says he wants to get married and have a family to impress her, and Robin begins dating a guy who seems to possess several canine characteristics.

In the aftermath of Ted and Zoey's break-up, Ted is having second thoughts. He is freaking out about an issue with the GNB headquarters, and historically when Ted freaks out about something, he turns to dating an old girlfriend if only for something comfortable and familiar, however bad returning to that relationship ended up being. When Barney and Robin find out that Ted is going to meet Zoey to get back together with her, they have to try and figure out where that meeting place is so that they can stop him. Beyond piecing together this puzzle, Barney and Robin's quest leads to them discussing their own relationship. Meanwhile, Lily has come down with a case of food poisoning from some soup. Marshall eats the soup three hours later, which means that his symptoms of excessive vomiting will start three hours later than Lily's did. Marshall has a job interview with a major environmental law firm in a few hours, and he is just hoping that he can make it through the interview without vomiting. Ted and Barney argue about which of them will have the pleasure of pushing the button when the Arcadian gets imploded. And one of these situation is the starting point for an imminent trip to the altar.

Ted tries to choose a date for the Architect's Ball, an embarrassing Internet video could cost Marshall a new job, and Barney makes a bold move to prove to Nora that he's a changed man.

Jealous over Barney's relationship with Nora, Robin tells her court-appointed therapist the series of events that led up to the assault that she committed.

Robin tries to date her therapist, Marshall thinks his boss has gone soft on environmentalism, Barney suspects that Nora may be lying about her age, and Ted takes his Intro to Architecture class on the worst field trip ever.

Kevin's declaration that everybody marries their parents ruins Marshall and Lily's romantic evening, but will anything keep Barney from getting lucky with Nora? And will Kevin finally get fed up with Ted and Robin's close relationship?

Barney and Robin are afraid to break the news to Nora and Kevin that they cheated with each other and want to get back together, while Ted and Marshall get stoned together at a concert.

In an attempt to deliver a devastating final slap to Barney, Marshall explains how he mastered the Slap of A Million Exploding Suns.