While Barney prepares for his wedding to a mystery bride, he and Ted reminisce about Punchy's wedding, including when Marshall and Lily announced they are having a baby. Meanwhile, Robin considers telling Barney she has feelings for him.
When Marshall gets the job of his dreams, he worries that, once the company discovers videos he made in the past, they may rescind the offer. Meanwhile, Ted can't decide who to bring to the Architects Ball.
After Ted runs into an old girlfriend, he tries to make amends with her since he cheated during their relationship. Meanwhile, Marshall and Lily make a bet with Barney that could force him to wear Marshall's ducky tie.
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 Marshall witnesses his boss's soft approach in settling with a million dollar company, he takes matters into his own hands. Meanwhile, Ted takes his architecture class on a field trip and things don't go as planned.
When Ted goes on a date without researching the girl on the Internet, the gang interferes, showing Kevin that they are too into each other's business. Meanwhile, Lily and Marshall come to terms with finding out the sex of their baby.
The gang begins to realize their romantic partner reminds them of one of their parents. Meanwhile, Barney and Nora's planned romantic evening is ruined by a string of bad events.
Ted finally meets his mystery girl in the Slutty Pumpkin costume. Meanwhile, Barney learns he is part Canadian, and Lily has pregnancy brain.
The gang reminisces about what happened during Hurricane Irene and Barney tries desperately to get out of wearing the ducky tie.
Barney and Robin find themselves in an uncomfortable situation when they hide a secret from their significant others. Meanwhile, Marshall, Lily and Ted attend a concert.
Ted and Barney discuss making a life-changing decision together, and Robin tries to discourage Marshall and Lily from moving to Long Island.
When Robin receives bad news, she decides to lie about it to the gang. Meanwhile, Marshall hangs Christmas decorations on the house in the 'burbs with help from his neighbor.
After celebrating New Year's Eve, Marshall visits his father's graveside to carry on their tradition of tailgating. Meanwhile, Barney and Ted open a bar called "Puzzles," and Robin is forced to fill in for an inebriated news anchor.
Lily and Marshall officially move to the suburbs and realize that Lily's bossy father refuses to move out of their house. Meanwhile, the gang adjusts to them moving by going to a strip club.
Lily and Marshall throw a housewarming party, where Ted nearly comes to blows with Marshall's boss, and Barney hits on a crazy divorcee.
For Valentine's Day, Lily and Marshall invite Robin and Kevin on a weekend getaway to Vermont, where Kevin and Robin discussing taking their relationship to the next level. Meanwhile, Barney realizes he has finally met his match.
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 tries to pursue Quinn, even after learning she is a stripper. Meanwhile, Marshall and Lily introduce Robin to life in the suburbs and Ted tries to figure out what to do with Robin's old room.
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.
Ted, Marshall and Barney embark on another "trilogy time," where they get together every three years to watch the "Star Wars" trilogy and envision what their lives will be like in another three years. Meanwhile Barney and Quinn move in together.
Just as Ted starts to settle into his new apartment alone, Barney tries to entice him into going out every single night. Meanwhile, Lily has a naughty dream about someone other then Marshall, and Robin finally becomes a famous news anchor.
When Lily and Marshall have a baby shower, Marshall starts to panic after realizing the baby is coming soon. Meanwhile, Ted and Robin come to terms with their relationship and Barney takes Marshall on a road trip.
While Marshall is in Atlantic City with Barney, Lily goes into labor, leaving him desperate to make it back to New York before the baby is born. Meanwhile, Ted and Robin try to distract Lily during her painful contractions.
On Barney's future wedding day, when his wife is finally revealed, the gang reminisces about the time they encouraged Ted to follow his heart and go after the one that got away.
