The Five find adventure when they spend Easter vacation at Mr. Lenoir's sinister house, Smuggler's Top. Set high above an eerie marsh, the house is honeycombed with hidden staircases and tunnels that once served as a hideaway for smugglers.

When strange lights begin to appear, the Five suspect that the tunnels are once more in use. What secrets does Smuggler's Top hold? Join Julian, Dick, Anne, George, and Timothy as they unravel the mystery!