"The Unknown" was the final entry in Columbia’s I Love A Mystery series. A woman hires two detectives to keep her alive long enough to claim her inheritance.
After three men are convicted of bank robberies, Charlie becomes suspicious. After some investigation Charlie finds the men are innocent and that the fingerprint evidence used to convict them had been forged. Charlie then proceeds to find the true bank robbers.
A young heiress finds evidence suggesting that at night she acts under the influence of a family curse and has begun committing ghastly murders in a nearby park.
London, 1761. St. Mary's of Bethlehem, a sinister madhouse, is visited by wealthy people who enjoy watching the patients confined there as if they were caged animals. Nell Bowen, one of the visitors, is horrified by the deplorable living conditions of the unfortunate inhabitants of this godforsaken place, better known as Bedlam.
An unsuccessful sculptor saves a madman named "The Creeper" from drowning. Seeing an opportunity for revenge, he tricks the psycho into murdering his critics.
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.
Stephen Neale is released into WWII England after two years in an asylum, but it doesn't seem so sane outside either. On his way back to London to rejoin civilization, he stumbles across a murderous spy ring and doesn't quite know to whom to turn.
Losing his memories of the last few days, neurologist Dr. Steele is told that his wife has been brutally murdered. Steele, aware of his conniving wife's infidelity, believes he may have been the killer and enlists the aid of his pretty nurse Stella to hypnotize him into recovering his lost memories.