First published in 1929, now public domain in the US and Canada. A house party is under way at the remote Black Dudley, and among the guests are some very shady characters. As they merrily recreate the ritual of the Black Dudley Dagger, Colonel Coombe dies. Pathologist George Abbershaw suspects foul play, and when a vital item is mislaid, a gang of crooks hold the guests hostage. Will they escape the house – what did happen to the Colonel – and just who is the mysterious Mr Campion?