Alistair Maclean had a knack for crafting compelling crime thrillers, and his adaptation of his own book contributes to this film’s merits, even though the overall production feels somewhat underwhelming. Anthony Hopkins portrays an agent sent by Robert Morley ("Sir Arthur") to look into the disappearance of a ship near Scotland's Northern coast. Upon reaching that isolated coastal area, he realizes his assignment is quite dangerous – something isn’t right. He soon meets the wealthy yachtsman "Sir Anthony Skouras" (Jack Hawkins), and immediately faces antagonism directed at him. Unfortunately, neither Morley nor Hawkins deliver performances up to their usual standard; however, Hopkins—along with the writer—does succeed in gradually developing a sense of momentum within the story, though the film often feels as bleak as the weather suggests. It struggles to find its footing. The plot contains too many unbelievable elements – and the conclusion, featuring a crossbow and a blowtorch, simply didn’t land effectively. The musical score is excessively loud (and the main theme becomes tiresome), and it's overly relied upon to generate or even enhance the limited suspense. It remains an enjoyable viewing experience, but primarily for some impressive underwater footage and attractive Caithness landscapes rather than anything substantial.

Source on TMDB