'There will be ten teacups at number 4, Berwick Terrace, W.8, on Wednesday, July 31st, at 5 p.m. precisely. The presence of the Metropolitan Police is respectfully requested.' The note was delivered to New Scotland Yard, its words evoking a cold murder case and its unsolved mystery of the ten teacups found beside the body. Scrambling to prevent a second killing, the police set up a watertight cordon at Berwick Terrace. But gunfire rings out from the top floor at 5 p.m. on the 31st, and the corpse of one of the celebrity tenants is found in a locked room, shot twice from behind, a smoking gun by their side and on the table - ten teacups. The killer has vanished into thin air, an impossibility which calls for the masterful sleuth Sir Henry Merrivale to enter the fray. First published in 1937, this classic mystery shines on today as one of the great masterpieces of the impossible crime genre.