Robin and Ted take advantage of Barney when he becomes "truth serum drunk," and Marshall does everything he can to remain in "pause" with Lily and avoid their fight.
While out looking for Barney on the day of the wedding, Robin and Ted reminisce about past relationships. Meanwhile, Marshall and Lily finally resolve their issues and Barney befriends two young guys eager to meet women.
Lily is concerned that Robin is not acting appropriately on her wedding day, Ted helps Barney pick his wedding suit, and the gang watch an embarrassing movie based on Ted's life.
The guys try to figure out where Lily went after her fight with Marshall and why. Meanwhile, after a talk with her mother, Robin is concerned that she is marrying her father.
With only half an hour to go, both Barney and Robin have panic attacks about their upcoming nuptials. Meanwhile, Marshall and Lily rewrite their old wedding vows.
After Barney and Robin's wedding, Ted builds up the courage to approach "the mother" at the train station. Meanwhile, three years after the wedding, Barney and Robin drop a bombshell on the group.
As the years go on, changes cause the group to drift apart, but they reunite one more time for Ted's wedding. Meanwhile, a monumental event causes Barney to finally change his ways.