[1] Pip, Bets, Larry and Daisy mistake Ernest "Ern" Goon, the village policeman's nephew, for their good friend Fatty in one of his disguises.

When Ern tells this to Mr Goon, the policeman asks the children's parents to ban them from solving another mystery.

The children then invent a fake mystery about kidnappers and robbers on Christmas Hill, hoping Ern will pass the information on to Mr Goon.

Ern sets out to follow him but goes in the wrong direction, along the road to "Harry's Folly", where he witnesses some mysterious voices, footsteps and lights.

Ern is rescued and promises to tear up a rude poem that Fatty wrote about Mr Goon.