Twenty-sixth in the long-running mystery series with Dr Launcelot Priestley.

At his residence in Beckenham in Kent on the outskirts of London, Sir Andrew Wiggenhall, the chairman of the board of directors of a large firm of ironmongers, is killed by an explosion that largely wrecks the house. Investigating officer Superintendent Hanslet is not convinced his death was an accident, particularly when another member of the firm's board is found dead. With the help of Priestley he sets out to solve the mysterious incidents that have beset the remaining members of the board.