A man takes an erection pill, planning to finally have sex with his girlfriend after she drinks an aphrodisiac. Instead, her adult sister accidentally takes it, the girlfriend falls asleep, and his erection refuses to fade. With the drugs working for eight hours, he and the sister lose control: his cock stays rock hard, her pussy turns soaking wet, and they ignore the girlfriend while pounding each other into a sweaty frenzy of repeated creampies.