Measures to exterminate rats in London were ineffective, and all because of the negligence and greed of individuals. And now the events of the first Invasion are repeated. But this time the rats have become smarter and almost no longer react to ultrasound, and poisons do not help. In addition, two-headed bald mutants have appeared again to continue to lead their relatives - black rats, born due to mutations caused by the consequences of nuclear tests. Now Pender, an employee of the Pied Piper company, has to find the lair of black rats in the forest in order to destroy them once and for all uninvited guests.