Attention, biting! Moscow around 1925: The highly regarded surgeon Professor Filipp Filippowitch specializes in rejuvenating procedures. But secretly, he experiments with dogs. With Lumpi, the street dog, the experiment finally seems successful: the dog mutates into a comrade in human form, but this "new human" is not in line with the bourgeois creator's intentions. For this abomination has not only inherited all the bad traits of its donor but also lives them out without conscience or responsibility. The desperate professor is left with no choice but to revert the transformation.