After Robin assaults a girl who is out to ruin Barney's relationship, she is forced to begin court-mandated therapy sessions. Meanwhile, Ted gets too involved in Lily's pregnancy.

When Robin breaks up with Kevin, Ted confesses his feelings to her. Meanwhile, Barney is on a mission to find something private of Marshall and Lily’s.

Barney continues his pursuit of Quinn. Ted has to deal with Robin's old room, while Robin gets a taste of suburban life from Marshall and Lily.

The gang tries to break up Barney and Quinn after learning they plan on moving in together, leaving Robin and Ted to fight over who deserves to sublet her apartment.

When Robin is hesitant to break up with Nick, Barney takes matters into his own hands. Meanwhile, Lily and Marshall are desperate for some private time.

Robin is determined to get Barney back no matter what it takes. Meanwhile, Ted fills in as Marvin’s Nanny, leading Marshall and Lily to realize that Ted is using baby Marvin to replace his other baby, the GNB building.

Barney's developing relationship with Patrice leaves Robin questioning his motives. Marshall's widowed mother gets back into the dating pool, but he thinks she may be swimming with a shark.

Robin takes steps to have Patrice fired from WWN, while Marshall puts a jinx on Barney. Later, Ted invites his architecture professor to the dedication of the GNB building, and Marshall and Lily bump into an oddball acquaintance from college.

Christmas approaches and Ted wrestles with whether to tell Robin about Barney's intentions involving Patrice, while Marshall and Lily get an early Yule gift, a night away from Marvin, but a case of separation anxiety strikes and threatens to ruin the evening.

While Barney works through his anger at Ted after finding out he still has feelings for Robin, Marshall Skypes in to act as a judge and help settle their dispute. Meanwhile, Lily realizes she is Robin’s only girlfriend.

When Gary Blauman shows up at the wedding, it sends the gang into a frenzy as they each recall an encounter with him.

With only a half an hour left before the wedding, Robin and Barney panic; Lily and Marshall rewrite their wedding vows.