Leonard and Sheldon encounter a young woman named Katie crying on the curb, having been left homeless by a break-up with her boyfriend. Leonard, despite Sheldon's objections, invites her to dinner and then to stay a few days at their apartment. She is abrasive, sexy, hard, and sarcastic, but she softens a little when she discovers that the guys aren't trying to get something from her. In the end, she decides she'll crash at their place for a while.