Murder Ahoy! (1964 film). Part 1 of 2.

The old wooden-walled battleship, HMS Battledore, has been purchased by a Trust for the rehabilitation of young criminals, and intended by the founder to "put backbone into young jellyfish." Shortly after joining the board of management of the Trust, Miss Marple witnesses the sudden death of a fellow trustee, who has just returned from a surprise visit to the ship, much disturbed by something he has discovered there.

Margaret Rutherford – Miss Jane Marple
Lionel Jeffries – Captain Sydney De Courcy Rhumstone
Charles Tingwell – Chief Inspector Craddock
William Mervyn – Commander Breeze-Connington
Joan Benham – Matron Alice Fanbraid
Stringer Davis – Mr. Jim Stringer
Nicholas Parsons – Dr. Crump
Miles Malleson – Bishop Faulkner
Henry Oscar – Lord Rudkin
Derek Nimmo – Sub-Lieutenant Eric Humbert
Gerald Cross – Brewer (aka Lieutenant Commander Dimchurch)
Norma Foster – Assistant Matron Shirley Boston
Terence Edmond – Sergeant Bacon
Francis Matthews – Lieutenant Compton
Lucy Griffiths – Millie
Bernard Adams – Dusty Miller
Tony Quinn – Kelly
Edna Petrie – Miss Pringle
Bill Dean - Police Constable
Roy Holder – Petty Officer Lamb
Henry B. Longhurst – Cecil Ffolly-Hardwicke
Desmond Roberts – Sir Geoffrey Bucknose
Ivor Salter – Police Sergeant
Arnold Schulkes – Officer
Paddy Smith – Steward