The Fox with a Velvet Tail (In the Eye of the Hurr (1971)

Ruth and Michel separate after Ruth finds another man, Paul. Ruth and Paul go to her sunny, idyllic beach side villa to spend summer. They are having a great time together, and then things start happening. The brakes of the car fail, and Ruth narrowly escapes death. The driving equipment goes faulty, and Ruth almost drowns. Michel turns up at their doorstep for an uninvited social call, and Paul asks him in. Ruth suspects Michel of being the person behind the mechanical faults of the car and the diving equipment, but Paul dismisses such a possibility - but he does suggest it to Michel. Then, the heat does go up.