Baffled by a drug smuggling case, private detective Fenton Hardy asks his teenaged sons Frank and Joe to keep a lookout for the criminals above Barmet Bay. The brothers are frightened away by a scream from a mysterious house nearby, but when their father goes missing, the budding sleuths and two friends investigate the caves beneath the house to save Mr. Hardy from the smugglers. In this 1927 mystery—the second in the series—these crooks mean business, and they are lying in wait for the meddlesome boys.