September 1888. A twenty-nine-year-old Arthur Conan Doyle practices medicine by day and writes at night. His first Sherlock Holmes story, A Study in Scarlet, although gaining critical and popular success, has only netted him twenty-five pounds. Embittered by the experience, he vows never to write another "crime story." Then a messenger arrives with a mysterious summons from former Prime Minister William Gladstone, asking him to come to London immediately.
Once there, he is offered one month's employment to assist the Metropolitan Police as a "consultant" in their hunt for the serial killer soon to be known as Jack the Ripper. Doyle agrees on the stipulation his old professor of surgery, Professor Joseph Bell—Doyle's inspiration for Sherlock Holmes—agrees to work with him. Bell agrees, and soon the two are joined by Miss Margaret Harkness, an author residing in the East End who knows how to use a Derringer and serves as their guide and companion.
Pursuing leads through the dank alleys and courtyards of Whitechapel, they come upon the body of a savagely murdered fifth victim. Soon it becomes clear that the hunters have become the hunted when a knife-wielding figure approaches.