Ted and Stella get engaged, but Ted soon learns that he doesn't know anything about her. Meanwhile, Barney confesses to Lily that he's in love with Robin.
Marshall claims that he had the best hamburger in the world during his first week in New York City, but he forgot where the burger joint is located. The gang then hits the streets of Manhattan to help him find it.
Ted tries convincing his friends that city living is much better than living in the suburbs by inviting them to Stella's apartment in New Jersey. Stella shocks him by announcing that she wants to live there permanently once they marry.
When Ted is packing his stuff for his move to New Jersey, he discovers that the gang was going to hold an intervention for his engagement to Stella and demands they hold it anyway.
Ted and Stella move up their wedding date, but the wedding may not go off as planned after Ted breaks the "No Exes Rule" and invites Robin to come in from Japan for the wedding.
When Ted unexpectedly runs into someone from his past, that he would rather have stayed forgotten, the gang starts wondering how they would handle it, if it happened to them.
Barney creates a holiday to celebrate not being a father. Meanwhile, Lily and Marshall are considering having a baby, but Lily first wants advice from Ted and Robin.
Robin meets back up with a group of over-indulging single party girls known as the "Woo Girls". Meanwhile, Barney receives a submission for design of the new company headquarters from Ted.
Ted walks into his apartment to Robin's date sitting naked on his couch. He learns about a technique that could revolutionize dating for the whole group, and everyone thinks about whether or not they should try it out that night.
Ted tries to prove to the gang that he's not a loser after being left at the alter. Meanwhile, Barney and Ted decide to pick a fight with the guys sitting in their favorite booth to impress Robin.
Ted tries to keep his irresponsible sister from hooking up with Barney during her trip to New York, and Robin starts hanging out with Marshall at a bar for Minnesotans, not telling them that she's really Canadian.
Ted and Robin discover that sex with each other solve their fights as roommates, which makes Barney very jealous and angry. Meanwhile, Marshall reveals that he's too embarrassed to use the office bathroom.
Lily comes back from a trip to Seattle only to run into a blizzard, which may threaten an airport ritual of meeting Marshall. Meanwhile, Ted & Barney offer to keep watch over the bar at MacLaren's while awaiting their dates, since Carl wants to close up early.
Robin discovers she must find employment within four days or be deported back to Canada, and agrees to create a video resume with Barney's help.
The gang thinks that Barney must have a secret girlfriend after noticing his bizarre behavior.
When Lily and Marshall get wind of the fact that Ted's college girlfriend has moved to New York, they decide to reveal to him how much they hated her.
When Karen comes across another woman's earring in Ted's bed, he learns that Lily put it there on purpose leading Ted to discover this isn't the first time she's covertly meddled in his relationships.
Marshall and Barney lie to keep Ted from finding out the headquarters he'd been hired to design for GNB has been cancelled.
When Barney learns Ted has a list of things he thinks the gang is too old to do, he sets out to do every task within 24 hours in order to prove Ted wrong.
Ted goes out on his own as an architect and hires an intern to help get things started, but the intern gets a little too close to others in the gang.
Ted breaks one of Barney and Marshall's relationship rules, texting a woman he recently met, so the pair play a joke on Ted by pretending to be the woman.
Ted explains to his future children how important it is to be in the right place at the right time. Meanwhile, Barney celebrates his 200th conquest.
Tony, Stella's fiancé, makes an attempt to ease the burden he feels for "ruining Ted's life", by helping him find a job, but instead proves that no good deed goes unpunished. Meanwhile, Barney wants to prove that he can get out of a speeding ticket.
Ted is trying to keep his architecture firm afloat by doing an all-nighter, but Marshall tries to lure him to the roof for a surprise 31st birthday party, on the fourth season finale.