"Why do they call you a dirty old man?" asks a cop of the bruised and battered Mr. Pegel at the beginning of Relations, which would have to rate as one of the better European sexploitation productions of its day. 
Pegel is a successful, middle-aged industrialist, enjoying a seemingly stable life with a doting but frigid wife. After being called out his factory in the middle of a stormy night, Pegel accidentally knocks down a pedestrian and is set upon by a gang of youths. Luckily, he’s saved by a pretty sixteen year-old redhead named Sonja, who quickly ingratiates her way into his life by showing up at his doorstep when Mrs. Pegel leaves town for a few days. Ignoring Pegel’s requests to leave, she brazenly hops naked into his bed. "I’ve never made it with anyone as old as you, but I’d like to try," Sonja whispers in his ear, before strapping him on and giving him the ride of his life.

At first reluctant to embark on any kind of serious affair, Pegel finds himself becoming more and more obsessed by Sonja (who looks very sleek and dominating in a full-length leather coat on the odd occasions when she’s actually clothed). They go to see a dubbed print of Barbarella (where the bored Pegel is set to leave until Sonja shoves his hand up her dress), indulge in a bathroom sex session, and visit a swinging discotheque until Sonja caps the evening off by treating her "Pappa" to a b.j. during the drive home!

But Pegel soon discovers that Sonja may not be all she seems when he finds some pornographic photos of her posing with Egon, the rugged young proprietor of a local cafe. Growing more suspicious, Pegel follows her to Egon’s cra