As Gus confronts Shawn over the diamond ring he just discovered, a valuable shipment of artifacts is stolen from a museum, so Shawn calls in Pierre Despereaux to help them catch the thief who stole the shipment. It turns out to be an old dagger that she was really after. As usual, nothing is what it seems when Despereaux is involved, and they discover that the dagger is the key to a much bigger mystery.