Susan's mother-in-law visits; Carlos and Gaby learn that their tenant is hiding a dark secret; war breaks out between Edie and Bree.

In the conclusion of the fourth-season finale, Katherine's secrets are revealed. But first, she begs off catering Bob and Lee's commitment ceremony, leaving Bree with her hands full. Meanwhile, Bob and Lee fight over the ice sculpture, and Tom Scavo steps in with advice; Orson keeps trying to win Bree back; Gaby gets a call from Ellie, who's on the lam; and Julie Mayer is accepted by Princeton, but Susan doesn't want to see her go.