The Hardy brothers' visiting Greek pen pal enlists their help in searching for a priceless ancient Greek helmet loaned to and lost by a Hollywood movie company years before.

Weird welcome -- Start worrying! -- Firecracker plan -- Trailed by an Amazon -- Tricky Leon -- Clue on film -- Mysterious red car -- Motorcycle monsters -- Disappearing act -- Flash flood -- Cheese bait -- Suspect Joe -- Los Angeles rendezvous -- Surprise phone call -- Cat and mouse -- Flight to Greece -- Masquerade -- Sympathetic vanides -- Caves of Corfu -- Bang-up roundup.