On a Boeing 747 flight from London to New York piloted by Captain Ernie Slade (Chuck Connors), a wealthy architect (Roy Thinnes) and his wife (Jane Merrow) have placed a druid sacrificial altar in the baggage hold of the airliner. Aboard for the ill-fated trip is ex-priest Paul Kovalik (William Shatner) and millionaire Glenn Farlee (Buddy Ebsen). Soon after takeoff, crew and passengers alike face the supernatural horror that is unleashed from the baggage compartment — the ghosts of the druids, seeking revenge from being uprooted from their ancient home.