While in a penal colony, Huguenot Jonathan Standish (Kerwin Mathews) is captured by pirates led by Capt. LaRoche (Christopher Lee) who force him to lead them back to his home village to retrieve a treasure supposedly hidden there.
- Kerwin Mathews ... Jonathon Standing
- Glenn Corbett ... Henry
- Christopher Lee ... Captain LaRoche
- Peter Arne ... Hench, a pirate
- Marla Landi ... Bess Standing
- Desmond Llewelyn ... Tom Blackthorne
- Oliver Reed ... Brocaire, a pirate
- Andrew Keir ... Jason Standing
- Michael Ripper ... Mack, a pirate
- David Lodge ... Smith
- Dennis Waterman ... Timothy Blackthorne
- Jack Stewart ... Godfrey Mason
- Lorraine Clewes ... Martha Blackthorne
- Jerold Wells ... Penal Colony Master
- Christopher Lee, Andrew Keir and Michael Ripper all appeared in another Hammer pirate film, The Devil-Ship Pirates, in 1964.
- Marla Landi appeared as Cecile Stapleton in Hammer Film Productions' The Hound of the Baskervilles, which also starred Christopher Lee.
The film was issued on a double bill with Mysterious Island - which was Britain's biggest grossing double bill of the year.