As the penultimate novel in the Famous Five series, it follows the usual formula of finding secret passages, drinking ginger beer, hunting treasure, and foiling evil-doers.

The Five climb into the ground of a supposedly empty stone house and find themselves locked in a strange cellar along with Wilfred and the stolen treasure.

The story closes with the Five lying sunbathing on a hillside near the holiday cottage, with all the local animals and birds gathering round to listen to Wilfred playing his flute.

[1] Lucas is thought to be based on the grounds man of the Isle of Purbeck golf-course, which Blyton's husband owned.

The film starred David Palmer (Julian), Amanda Coxell (George), Darryl Read (Dick), Paula Boyd (Anne), and Michael Wennink (Wilfrid).