Suzanna Leigh ... Vicki Robbins
Frank Finlay ... H.W. Manfred
Guy Doleman ... Ralph Hargrove
Catherine Finn ... Mary Hargrove
John Harvey ... Insp. Thompson
Michael Ripper ... David Hawkins
Anthony Bailey ... TV Compere
Tim Barrett ... Det. Harcourt
James Cossins ... Seagull Island Coroner
Frank Forsyth ... Seagull Island Doctor
Greta Farrer ... Vicki's Sister
Katy Wild ... Doris Hawkins
Gina Gianelli ... Secretary
Michael Gwynn ... Dr. George Lang
Maurice Good ... Vicki's Agent