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.
Robin is nominated to receive an award for a news report and everyone needs a date to take to the show. Barney introduces Ted to Mary as a date that Ted can take to the show. Originally Ted is opposed to the idea of just trying to save face in front of Robin but when she shows up with a date he changes his mind. Robin asks Mary lots of questions, and Ted begins to really like Mary, despite her occupation.
As Lily becomes more of a permanent fixture in the apartment, Ted feels like he is being edged out of the mix by his engaged roomies. Petrified of being left alone and homeless, Ted tells Marshall that when he and Lily are married, he wants the apartment. The problem is that Marshall wants to keep the place too, so they settle it like real "grown-ups" -- launching into a sword fight that leaves one man down for the count.
When a matchmaker with a 100% success rate turns Ted away because he is not compatible with any of the available women in her database, he is still determined that he is going to find his match. After getting information from the matchmaker’s computer, Ted pays a visit to a very cute, but taken, dermatologist in an effort to prove the prediction wrong that there are no women out there for him. Meanwhile, Marshall and Lily are obsessed with ridding their apartment of a critter.
When Ted's best friend Marshall proposes to his girlfriend, Lily, Ted realizes he'd better get a move on if he hopes to find true love. Ted soon meets Robin in a neighborhood bar, immediately becomes smitten and scores a first date. But when Ted can hardly wait to see her again, his eagerness threatens to scare her away.