[1] During a school holiday, the children are told by their parents to spend their time visiting sites in the surrounding countryside, rather than searching for mysteries in their village of Peterswood.

The children visit an old stately home, Banshee Towers, that is exhibiting famous sea paintings, which Ern and Bets love.

On a subsequent visit, Ern spots that a small boat he admired on one of the paintings is missing.

After investigating, they discover the owner of the Towers has been conspiring with an art forger and a second member of staff, to replace the collection with copies and sell the originals.

The mystery is not divided up by assigning investigative tasks to each of the five children as was normally the case and Fatty more or less solves this one on his own.