With mauled bodies appearing on Liverpool streets, rumors circulate that the culprit might be an inhuman monster known as Spring Heeled Jack. Determined to debunk the city's superstitions, Holmes delves into the criminal underworld, piecing together an intricate and deadly puzzle. Meanwhile, Dr. Watson witnesses the creature with his own eyes, and sets out alone in pursuit. Will Holmes be able to save his dear friend from the perils beneath Liverpool?