One of Richard West's overseas students disappears. Her friends think Boon has been forced into the sex trade. They enlist Richard's help in finding Boon, who is believed to be held captive in a remote mountain resort, The Tall Oaks. The lecturer and a friend and two students are themselves captured, leaving Richard, Alex and Policewoman Rebecca Nolan to rescue them before they are disposed of. Boon is thrown into a raging torrent to drown by one of the merciless criminals.