Waldemar Weber, a well-meaning paediatrician, is haunted by his past: As a student, he married his landlady in order to help her to legitimate her misbegotten son. Today, Waldemar is married to another woman, who doesn′t know about this generous deed and his adopted son. Therefore, he is quite embarrassed, when the now grown-up Egon unexpectedly appears at his doorstep. And as if this weren′t enough commotion, the trained animal trainer brought along three chimpanzees. Now poor Waldemar has to come up with a plan how to explain Egon′s existence to his wife while also hiding the lively apes from her.