Not popular on its small first release this wonderful and genuinely beautiful thriller is great adventure and well cast. Set in 1901 off the sandbanks near the Fresian Islands near Brussells/Germany /Holland RIDDLE is an atmospheric foggy 'chums in peril' mystery with a spunky cast and sublime and eerie sailboat thrills. The woolly jumpers alone should have won an award! York and MacCorkindale are almost interchangeable but the always gorgeous Jenny Agutter is as usual irreplaceable and perfect. MacCorkindale even leaps overboard one morning all nude, just to liven up the visuals! Filmed in panavision this really suffers on TV and deserves a DVD release to allow a whole new generation to soak up what is a generally unappreciated but lovely sailing thriller. The art direction and atmosphere is so accessible it is almost enough reason to just let yourself sail away. It is one of my favorite films and patient viewers will be well rewarded. It seems to be screened constantly on late night Australian TV, and even has an extra scene early in the film as Michael York arrives by train. RIDDLE OF THE SANDS is one of the most absorbing and beautiful Edwardian/Victorian era films made in Britain in the 70s.