Sometimes the most ordinary... cat is enough to solve a complicated case. And if the cat is not ordinary, then the prospects for discovery increase significantly. Investigator Boris Veresen, who unexpectedly became the owner of a St. Petersburg sphinx named Mandarin, is convinced of this. And the murder that they both have to investigate will turn out to be only the final link in a chain of other crimes, the threads of which stretch into the past. And this chain starts to move because of one single pebble, moved by a cat's paw...