Grey Mask is a mystery novel by Patricia Wentworth. It is the first book in her series featuring the private investigator Miss Maud Silver. The novel opens with Charles Moray returning to England after being away for four years, following a broken engagement. He discovers that his family home has been infiltrated by a criminal gang led by the enigmatic and sinister figure known only as the "Grey Mask." Unbeknownst to the gang, Charles overhears their plans for a sinister scheme involving an inheritance and the manipulation of a young heiress named Margot Standing.