Walden thinks his girlfriend is cheating on him; Alan starts dating Larry's sister, Gretchen (Kimberly Williams-Paisley).

Lyndsey finds out about Alan's relationship with Gretchen; Walden has a difficult time telling Barry to find his own place.

Walden gets an invitation to his ex-girlfriend's boutique opening. Meanwhile, Gretchen wants to spend more time at Alan's (a.k.a. Jeff Strongman) house.

After reconnecting with Kate, Walden becomes convinced she is the one for him -- until he meets a woman named Vivian (Mila Kunis).

Alan's girlfriend, Gretchen, insists he confess his true identity to Larry. Meanwhile, Walden goes on a road trip with Jenny and Barry to see his first car.

Alan must face the consequences after revealing his identity to Larry.