After signing up to be a Big Brother to a young boy, a mix up pairs Matthew with another adult named Danny. But Matthew doesn't see anything unusual about their relationship, and Danny realizes that Matthew is in need of someone to look after him. Meanwhile, after Dave reassumes control at the office, a leotard in Lisa's old desk convinces Bill that she's dating someone. And after Dave finds a pair of movie ticket stubs there, too, Bill concludes that it's Beth. Though Dave is reluctant to believe it, Joe agrees with Bill. And a surveillance videotape from the lobby convinces Jimmy, Bill and Joe that Lisa has been spending the night with someone. Meanwhile, when he and Danny are reluctant to break off their Big Brother-Little Brother relationship, Beth claims to have been Matthew's Big Sister for more than two years. But after they both take Matthew to the zoo, it's Danny and Beth who really hit it off. After spotting Danny and Beth kissing at the zoo, Matthew makes his way back to the office alone. And while she tries to cover by claiming they were looking for him, Beth still must agree to spend an entire day with Matthew. After a search of Lisa's phone records fails to identify her new lover, she and Dave are forced to admit that they've been sleeping together. And, finally, Lisa lets Dave know that, even though he has a date, she'll be waiting back at his apartment in order to have sex again.