The Curious Dr. Humpp

A doctor, obsessed with human sexuality, abducts couples in the midst of intimate moments and holds them captive in his mansion. He injects them with a serum to amplify their sexual desires, then forces them to engage in sexual acts while he harvests a mysterious fluid from their bodies. This fluid is crucial to preventing his own transformation into a monstrous creature, as instructed by a disembodied brain that guides him.