The Mystery Files of Shelby Woo (1996)

S2E7 The Case of the Knockout Gas

Convenience stores in the "Reddy Eddy" chain are mysteriously being infiltrated with a gas that renders the employees unconscious for a short time. When they regain consciousness, they find that no items have been taken! Is this an act of vengeance or merely a prank? Complicating matters for Shelby is her burgeoning crush on the son of one of the primary suspects in the case.