Bodies in Heat (1983)

Laura, a beautiful woman, afraid that her husband, Lawrence is trying to kill her tries to enlist Harry as her own private detective. She is in need of a giant favor. At first, he's reluctant, but he finally gives in when she offers him more than just money. From then on, the action gets even hotter as they revel in the depths of their own sexual splendor, and plot to dispose of her husband for good.