In London, Dr John Watson convalesces, after his disastrous Afghan war experiences. Sharing rooms with an enigmatic, new acquaintance, Sherlock Holmes, their quiet bachelor life at 221B Baker Street is short-lived. A dead man is discovered in a grimy house in south-east London. His face contorted with horror and hatred. On the wall, the word 'rache' - German for 'revenge' - is written in blood, yet there are no wounds on the victim or signs of a struggle. Watson's head is in a whirl, but the formidable Holmes relishes the challenge - and a famous investigative partnership begins.