Erin and Aaron's first day as step siblings and they are in no mood to get along. But when they discover that their differences may lead to a family break-up, they must find a way to come together.

Aaron finds the perfect replacement for his beloved broken piano but the shop owner, Mr. Ledder, has a history with Erin and refuses to sell the piano to an instrument killer like her.

Erin and Aaron clash over Saturday night traditions: Erin wants pizza and Aaron wants sushi; Chuck and Natasha have a special daddy-daughter day planned but struggle to find a shared activity they'll both enjoy.

Erin invites Aaron's old friends and teammates, the Yellow Jackets, to visit him, not realizing Aaron never told them about his love for music; when Aaron lies to his friends, Erin has to convince him to come clean.

With Erin in New York, Aaron is forced to play Porchfest solo. But Aaron can't write songs without Erin, and Erin only wants to perform with Aaron.