Four British teens on vacation visit an island and discover that a terrorist group is using it as their headquarters.

Norman Bowler
as Bill Smugs

Wilfrid Brambell
as Uncle Jocelyn

Eleanor Summerfield
as Aunt Polly

Catherine Schell
as Alison Mannering

John Rhys-Davies
as Smith

Leon Lissek
as Jo

Paul Williamson
as M.I.5 Boss

Frank Williams
as Map Shop Owner

Peter Forbes-Robertson
as Mr. Roy

Julie Neesam
as Maggie