While off-world, Wallace's teammate Babbis fell 20 feet into a brook. Attempting to help his friend, Wallace lost his own footing and broke his ankle. Back at Stargate Command, General Hank Landry asked that the team debrief him after Wallace left the infirmary.
Later Wallace, now on crutches, found himself encountering Sheppard's Atlantis unit while on his own way to Landry's office. About to retake Atlantis without the General's authorization, Sheppard stunned his teammate with a zat'ni'katel and stowed his body in a storage locker.
The Return, Part 1 - Fearing Sheppard will insist he be replaced, Wallace is disappointed to find the colonel about to commence a mission without him.