In "Travels with Scout", Dylan realizes that he is moving to Portland because his parents are getting back together. Cameron hears this and offers himself to replace Brian. His audition is initially bad, but tells Dylan, Neil, and Craig, that he "was holding the sticks in the wrong hands" and when he put them in the other hand, he proves to be a very capable drummer.
When Mitchell finds out, he is annoyed since they are going to a party the same day and asks him to cancel the concert. Cameron says no since he always stays with Lily so Mitchell decides to go to the concert then the party. Mitchell ends up staying at the concert, admitting Cameron was amazing, although Cameron plays a drum solo that is far too long.
Afterwards, Brian returns since his parents separated again. Cameron thinks he is going to stay but soon realizes that he is the one that is going to leave.