The Ashcombe Deed Safe

At Ashcombe Manor, the family deeds sit locked inside a brass safe — and the master of the house, the only one who knew the code, died last week without writing it down. The deeds must be shown at a court hearing on Monday. Without them, the family loses the manor. But the housekeeper kept a ledger: for years she wrote down the test combinations the master dialled to check the lock, and the numbers the safe answered back. From her notes alone, the code can be worked out — and the safe opened in time.

Points for solving; rating never moves in free play.