Lily, Barney and Robin attend a high school prom to scout out a potential band for Lily and Marshall's wedding reception. In order to get in Lily and Robin pretend to be the dates of two kids who were going alone. Ted and Marshall are back at the apartment where they are preparing the invitations to be sent out.

With everything going wrong on Lily and Marshall's wedding day, to everyone's surprise it's confirmed bachelor Barney who tries to fix it all.

Marshall and Lily are less than thrilled when they hear that Ted's college girlfriend (Laura Prepon) has moved to New York.

When the gang tries to convince Ted that he is being strung along by Tiffany, they reflect about relationships where each of them has been in the same situation.

When the gang goes to a black tie event at the Natural History Museum, Ted gets introduced to Zoey's husband, The Captain.

Marshall takes on his old friend/new nemesis Brad in the biggest case of his career. Meanwhile, the gang reminisces about their own run-ins with the law, leading to a debate over who was the biggest delinquent as a teenager.

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