In this thrilling urban fantasy mystery, the iconic duo of Sherlock Holmes and Dr. John Watson find themselves embroiled in a case like no other. Londoners are being savagely attacked and killed, and the evidence suggests that something extraordinarily large and dangerous is responsible. As they delve deeper into the investigation, Holmes and Watson find themselves descending into the dark and dangerous depths of the city's underground tunnels. What they uncover there is both horrifying and deadly, as they confront a monstrous creature unlike anything they have ever encountered. With time running out and the body count rising, the two detectives must use all their skills and cunning to solve the case and bring the killer to justice before it's too late.