When her boss raises the question of who Zack really is, it prompts Billie to go on a fact-finding mission as to the true identity of her baby's father.
Billie's pregnancy creates an attraction from members of the opposite sex, while Billie feels her own results of her hormonal changes, but she becomes really befuddled when Zack rebuffs her advances.
Billie declares that she and Zack are able to see other people, but it's Billie who finds the dating scene a little rougher than expected, and Zack finds a conscience when he tries the waters, too.
Billie tries to live vicariously through Zack and Davis by offering up dating advice to them. However, things take a turn, when the objects of the boys' affection reveal their true intentions.
Billie unintentionally causes Abby and Nick to break up when she asks them to be Godparents. However, after a fun night on the town with Davis goes too far, Billie must stop Abby before she does something she will regret.
When Billie and Zack take instructional parenting classes separately due to their schedules, Billie goes with Olivia and Abby. However, the course quickly becomes a competition when Abby outshines Billie at all the tasks.
Worried that she'll ruin Christmas - as she has in previous years - Billie tries to hide from her parents the fact that Zack is living with her. Meanwhile, Abby's husband, Nick, tries to impress their father.