The novel centres on the mystery of who could have set fire to Mr Hick?s cottage.
The five children, Larry and Daisy Daykin, Pip and Bets Hilton, and newcomer Frederick Algernon Trotteville (later nicknamed Fatty from his initials), meet at the scene of the fire and end up solving the mystery together.
Their suspects include an old tramp, a dismissed servant, a hostile colleague, and the cook.
They find certain clues: Broken-down nettles in a ditch, a footprint in a grassy field, and planes (which Mr. Hick mentions "flew over" the other day).
The children realise that as Mr Hick claims to have been in the London train when the cottage was burnt, but by his own report he saw the planes which flew over the village at the same time, he is contradicting himself.
Fatty finds out that the cottage and the burnt papers Mr Hick describes as 'most important' were insured. The children deduce that Mr Hick burnt his own cottage for the insurance money.
The book also introduces Inspector Jenks, who turns out to help the children and becomes a good friend of theirs.
(Age Range 9-12)