Ted convinces Victoria to take a brief detour before they leave together after she leaves her fiancé at the altar, and Barney's engagement to Quinn may be short-lived after she finds about his past relationship with Robin.
When Lily and Marshall have trouble finding a nanny, they learn it's because of an elaborate scheme Barney came up with to meet girls. Meanwhile, Robin and Ted butt heads over who has a more serious relationship.
As the season of break-ups continues, Ted and Victoria must choose the next step in their long and complicated relationship. Meanwhile, Robin worries about Barney when he chooses a dog to be his wingman.
Robin has a plan to get Barney out of her system for good, Ted witnesses Marvin's first crawl while babysitting for Marshall and Lily, and Barney has a new business idea after destroying a beloved tie.
Robin tries to get Barney's "Playbook" out of jealousy over his new girlfriend, Marshall catches his mom having sex with Lily's dad, and Ted tries to get everything back that was borrowed from him and never returned.
Ted wants to rub his new building in the face of an old professor, Barney is the victim of a lengthy jinx, Marshall and Lily run into an annoying old acquaintance, and Robin gets an opportunity to fire Patrice.
Will Ted go to the opening of his new building with Robin as his date, or will he break his promise to Barney and tell her that Barney is proposing to Patrice? Meanwhile, Marshall and Lily have big plans for a rare night out.
Barney convinces Ted to sleep with a 20 year old until Barney learns her identity, Robin discovers that her engagement ring makes her invisible, and a leather cuff improves Marshall and Lily's love life.
Robin's past as a Canadian pop star is revisited when Barney uncovers the lost episode of a music documentary series in which she was featured as Robin Sparkles. Marshall and Lily have some concerns about Ted's latest girlfriend.
It's weeks before Barney and Robin's wedding, and one of the many things they still have to decide is where to live. The one thing Robin insists is that they don't live at Barney's apartment. So it goes on the market. However, Barney doesn't want to sell it to just anyone, but someone who is worthy of what was and will always be in his heart his "Fortress of Barnitude". Robin has a slightly different idea, which isn't as easy to achieve as she would like when she and others learn more and more about with what Barney has equipped his apartment. Meanwhile, Lily hasn't ...