Ilya Smagin, a police captain, has lost his partner and friend – the dog named Ragdai, one of the best search dogs in their dog service – during a special operation.
Smagin and his colleagues are hunting down a gang of drug-dealers and trying to find out where they are hiding the dope.
Smagin believes he will never find a match for Ragdai. Then he receives a message from a colleague of his, who was killed during the same operation. Anticipating his own death, the colleague begged Smagin to take care of his dog. Lusha misses her owner badly and wouldn’t take any food. Smagin takes Lusha to his home.
The dog turns out to have a unique sense of smell, but to be a hard nut as well.