Lizzie and Sam visit a gay bar with Tyler, and argue about Sam's penchant for unavailable men. Lizzie flirts with gay boy Mark and gets drunk; he takes her home and has sex with her. Lizzie tells Sam of the encounter and the two friends ponder how to tell if a guy is straight or gay. Sam is curious about Devon, a cute new co-worker, but picks up mixed clues to his orientation from his conversation, computer search history, and behavior. They host a launch party at a tattoo parlor for b**chy client, Fiona's, photo book. Sam invites Tyler to see if he can get a read on Devon, but even Tyler is stymied. Tyler is delighted with the b**chy Fiona, though, and surprises Lizzie and Sam by having sex with her in a back room. At the party's end, Sam flat-out asks Devon if he's straight or gay. He suggests she check his relationship status, which leaves the matter unsettled: Devon is involved with "Chris." Lizzie finally gets an answer to her questions about Mark when she discovers that he is actually straight, and masquerades as gay to get women. Sam resigns herself to never being sure about Devon. Both women are confused by Tyler, who says that despite having had sex with Fiona, he's absolutely sure he's one hundred percent gay.