| Director | Peter R. Hunt |
|---|---|
| Budget | £1 million |
| Box office | £454,538 |
Johannesburg, 1973. A tunnel collapse at the Sonderditch gold mine is no accident. It was actually a failed plan by an international syndicate to manipulate gold prices. They now arrange for a hole to be drilled into Sonderditch's underground wall next to a huge water reserve. Presumably, when the wall is breached, a flood will result, destroying the mine and boosting gold's market value. The syndicate's membership includes the mine-owner Hurry Hirschfeld's grandson-in-law, Manfred Steyner, so this should all be a done deal. But Steyner's chief accomplice, his general manager Frank Lemmer, died in the tunnel collapse. So he now interviews Rodney "Rod" Slater, the underground manager, for the vacant post.
Afterwards, Slater meets Steyner's wife Terry and is attracted but she shows no interest. However, Steyner arranges for them to meet again, hoping Terry will influence her grandfather Hurry, Sonderditch's owner, to endorse Slater. The plan works: Slater becomes general manager and he and Terry begin an affair.
Slater, unaware of the syndicate or its plans, carries out Steyner's orders to drill near the reservoir. But to provide insurance against catastrophe, he plants a safety charge to block the tunnel in case of a water breakage. Steyner soon discovers Slater is seeing Terry but allows the affair to continue: it will keep Slater away from the mine so that the safety charge can be disabled without his knowledge.
Over a warm Christmas, Slater and Terry pilot her small plane to a vacation spot. While they are away, drilling back at the mine continues. When the final breach is made, a wall of water roars into the mazes of tunnels and shafts. The mine then floods, trapping a thousand workers. Slater hears of the disaster on the radio and demands Terry fly him back to the mine. Once there, Slater and Big King, a trusted indigenous worker, descend into the mine, braving flood waters, to reconnect the safety charge that will seal the dike and save the trapped miners. They succeed, but only because Big King sacrifices his own life to detonate the charge, allowing Slater to fall injured into a rubber dinghy and float to safety.
As Slater is carried from the mine to an ambulance, Hirschfeld tells him, "You're a maniac!"—but with a satisfied smile. Terry adds, "I love you." Meanwhile, after Steyner's plot to destroy Sonderditch has failed, he is targeted for assassination by the syndicate. He perishes after being run over by co-conspirator Stephen Marais commandeering Steyner's own car; Marais also loses his life when Steyner's car explodes after Steyner threw a stone at Marais, smashing his car's windshield. Steyner's death leaves Terry free to continue her relationship with Slater.