Terror by Night (1946)
Holmes and Watson board a passenger train bound from London to Edinburgh, to guard the Star of Rhodesia, an enormous diamond worth a fortune belonging to an elderly woman of wealth; but within the first hour of the trip, the woman's son is murdered and the diamond stolen and any of the passengers in their car could be the killer thief. mathematics, black and white, private detective, jewel theft, gin rummy, sherlock holmes
ETC.
