Set in Toronto, Canada in the late 19th century, Murdoch Mysteries is based on the best-selling novels by crime writer Maureen Jennings and follows the adventures of Detective William Murdoch (Yannick Bisson) who uses innovative inventions and pioneering forensic techniques to crack cases, aided by the enthusiastic but slightly naive Constable George Crabtree (Jonny Harris) and gruff but good-hearted boss Inspector Brackenreid (Thomas Craig).
In series 4, Murdoch's soulmate, pathologist Dr Julia Ogden (Hélène Joy), decides to start afresh in Buffalo, New York where she meets the handsome Dr Darcy Garland. Will this finally put paid to Murdoch and Ogden's troubled romantic relationship?
Julia's replacement at City Morgue is Dr Llewllyn Francis (Paul Rhys), an officious pathologist from Scotland Yard who has no interest in new forensic techniques and disapproves of Murdoch's habit of calling the coroner to the crime scene. Suffice to say, he's no Dr Ogden!
Intriguing mysteries to be solved this series include a young schoolgirl who is discovered dead with considerable blood loss in the midst of a vampire craze created by the recent publication of Bram Stoker's Dracula, a dashing, modern-day Robin Hood who pulls off daring bank robberies to give to the poor and a switchboard operator who overhears an apparent murder, leading Murdoch to develop some new wire-tapping technology.
And, when a man is murdered at an Alice in Wonderland costume party, all the evidence points to the guest dressed as the Mad Hatter... who just happens to be William Murdoch himself!
Along the way, Murdoch discovers his long-lost sister, is reunited with Anna Fulford (Lisa Faulkner), the beautiful barmaid he met in Bristol in the third series and gets involved in a matter of national security when he discovers a trail to lost treasure from the American Civil War.