A year after the events of the previous opus, it seems that the past has come to titillate the Sombresbois family. A special organization decides to lure them by taking hostage the survivors of the previous opuses, those whom the family spared because they were innocent, by taking them to the basements of a secret underground laboratory in London. However, the mysterious "Mr. Smith"'s plan for revenge may well backfire, as his lair's defenses won't be enough and his "secret weapon" may surprise him !
