It centres on William Murdoch (Yannick Bisson), a detective at Station House Four, who solves crimes using scientific techniques and inventions which are highly advanced for the time (e.g. fingerprinting).
These featured a different cast: Peter Outerbridge as Murdoch, Keeley Hawes as Doctor Ogden, Matthew MacFadzean as Constable Crabtree and Colm Meaney as Inspector Brackenreid.
[5] Recurring cast members include Tamara Hope as Edna Garrison, Dmitry Chepovetsky as Nikola Tesla, Lachlan Murdoch as Constable Henry Higgins, Arwen Humphreys as Margaret Brackenreid, Allan Royal as Chief Constable Stockton, Geraint Wyn Davies as Arthur Conan Doyle, Maria del Mar as Sarah Pensell, Stephen McHattie as Harry Murdoch, and Peter Keleghan as Terrence Meyers.
[8] Recurring cast members include Lachlan Murdoch as Henry Higgins, Arwen Humphreys as Margaret Brackenreid, Paul Amos as Doctor Roberts, Sarah Gadon as Ruby Ogden, Michael Seater as James Gillies, Peter Keleghan as Terrence Meyers, Sarah Allen as Enid Jones, Dakota Goyo as Alwyn Jones, and Stephen McHattie as Harry Murdoch.
[12] Recurring cast members include Lachlan Murdoch as Henry Higgins, Lisa Faulkner as Anna Fulford, Allan Royal as Chief Constable Stockton, Richard Clarkin as Inspector Davis, Arwen Humphreys as Margaret Brackenreid, Paul Amos as Doctor Roberts, Peter Stebbings as James Pendrick, Kate Greenhouse as Sally Pendrick, Sarah Gadon as Ruby Ogden, Dmitry Chepovetsky as Nikola Tesla, and Peter Keleghan as Terrence Meyers.
[29] Part of the festivities of the day included a Victorian era costume competition with the winner getting a role in an episode of Murdoch Mysteries.
[90] Season 9 will see guest appearances of Lucy Maud Montgomery, Prime Minister Wilfrid Laurier and Mouna Traoré as Rebecca James, a young protegee whom Julia takes under her wing.
[132] Dylan Neal reprised his role as Jasper Linney, Murdoch's half brother, during the Christmas special, last seen in the season two finale.
In episode four, Shanice Banton joined the cast in a recurring role as Violet Hart, a medical student and Julia's new morgue assistant.
[153] Former Canadian Olympic figure skater Elvis Stojko guest-starred in episode 13 as ex-con Sam Marshal, who Murdoch suspects of murder.
[173] This season, Murdoch Mysteries celebrated its 200th episode, with Lisa Norton, John Tench, Dmitry Chepovetsky, David Storch and Peter Stebbings, reprising their roles as Emma Goldman, Alexander Graham Bell, Nikola Tesla, Thomas Edison, and James Pendrick respectively.
[174] Colm Feore made a guest appearance this season as George's long lost father, George Crabtree Sr.[175] This season sees the return of Peter Keleghan, Peter Stebbings, and Matthew Bennett as Terrence Meyers, James Pendrick and Allen Clegg, respectively for a total of eleven episodes.
Returning recurring stars include Nigel Bennett as Chief Constable Giles, Jesse LaVercombe as Jack Walker, Colin Mochrie as Ralph Fellows, Peter Stebbings as James Pendrick and Peter Keleghan as Terrence Meyers, with Keleghan's wife, Leah Pinsent, guest starring, playing his TV wife.
Peter Stebbings returns as James Pendrick in episode fourteen and guest-stars alongside astronaut Chris Hadfield, portraying a rocket scientist, for the event of Halley's Comet.
Olympic gold medal winner Andre De Grasse makes his first television appearance as a shopkeeper who brags how he fast he could run.
Episode eleven deals with the Highland Games and was written by Maureen Jennings, with guest stars R. H. Thomson and Ian D. Clark as Scotsmen from different clans, both of whom co-starred in Road to Avonlea.
Episode thirteen sees the return of both Colm Feore as George Crabtree Senior and Sarah Swire as Dorothy Ernst.
Ted Atherton, who co-starred with Yannick Bisson in two TV series, guest stars in episode sixteen as Preacher Jimmy Wilde.
Season 18 has a new opening scene, the first time since Murdoch Mysteries started, with only the main cast's names being shown when they appear in an episode.
Etalk's Lainey Lui appeared in episode twelve as a gossip columnist and grand opening of the Royal Ontario Museum.