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.

Basil Rathbone
as Sherlock Holmes

Nigel Bruce
as Dr. John H. Watson

Alan Mowbray
as Major Duncan-Bleek

Dennis Hoey
as Inspector Lestrade

Renee Godfrey
as Vivian Vedder

Frederick Worlock
as Prof. William Kilbane

Mary Forbes
as Lady Margaret Carstairs

Skelton Knaggs
as Sands - Moran's Accomplice

Billy Bevan
as Conductor Taking Tickets

Geoffrey Steele
as Roland Carstairs
CinemaSerf
A wealthy young aristocrat employs "Holmes" to escort himself and his mother on a train from London to Edinburgh alongside the legendary Star of Rhodesia - a diamond the size of a duck egg. Together with trusty sidekick "Dr. Watson" and "Insp. Lestrade" who is ostensibly off fishing for salmon (it i...