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"Invention Convention" is the ninth episode of the fifth season of the Murdoch Mysteries and the sixty-first episode of the series. It first aired on April 24, 2012 (UK).


Detective Murdoch investigate the shooting death of inventor Karl Schreyer who was shot at an inventor's convention. He was very much disliked by his fellow inventors who accused him of stealing their ideas for his own use. He had contacted Murdoch after receiving a threatening note and he was there when Schreyer was shot giving his thank you speech for winning the Eaton Prize for most commercially viable invention in this case, a vacuum cleaner. Murdoch's biggest problem is to figure out just how an assassin could shoot him without being seen. While the evidence points to other inventors as responsible for the murder, an invention by Alexander Graham Bell provides the solution to the crime. Meanwhile, Constable Crabtree tries to commercialize some of Murdoch's inventions, while Inspector Brackenreid has a toothache and tries to skip his dental appointment.

Character Revelations

  • Crabtree believes so much in Murdoch's inventions, he has taken a booth at the convention to demonstrate The Truthizer (108) in hopes of winning The Eaton Prize for the Detective.
  • Murdoch tells George that his creations are not inventions but re-workings of known technologies.


Historical References

  • Charles Babbage's difference machine was developed in the 1820s.
  • Reference to Eaton's department store
  • Alexander Graham Bell, beside being known for his inventions, was also known for his work with the deaf.
  • The phonograph cylinder was patented by 1878.
  • Heroin had been trademarked and marketed as an over-the-counter drug by Bayer since 1895.


  • Dr. Julia Ogden does not appear in this episode.
  • The Pneumograph (lie detector) voted #1 of 5 Favorite Murdoch Mysteries Invention by The Arts Guild 8/20/2015 Adnan M.
  • At the end of the episode when George Crabtree suggest that a sound activate device could be used to turn the lights on and off, it is a reference to the real life device: The Clapper.
  • The decoded text of the cypher actually reads "It is essential that we are all seen to be watching the speech the instant the machine fires. We have precisely 20 seconds between when the device is triggered and when the shot is fired. Should the machine be discovered it is imperative that we stick to the plan. We must hang together or we will hang separately."
  • A future sequential killer will replicate the murder mechanism in Manual for Murder and George will reference this case in The Final Curtain.
  • Canadian businesswoman and investor Arlene Dickinson is also known for her appearance on the Canadian franchise of Dragon's Den.


  • The secret message Murdoch is trying to decode doesn't contain spaces. The copy on his blackboard contains spaces. They are not random, as it's those spaces which are the key for Murdoch to be able to find the key by noticing several occurrences of the three-letters word "GND" and supposing it's the coded word "THE".


Main Cast

Yannick Bisson as William Murdoch
Hélène Joy as Julia Ogden
Thomas Craig as Thomas Brackenreid
Jonny Harris as George Crabtree
Georgina Reilly as Emily Grace

Recurring Cast 

Arwen Humphreys as Margaret Brackenreid
John Tench as Alexander Graham Bell

Guest Cast

Arlene Dickinson as Miss Dickinson
Jonathon Young as Ernest Harding
Carlos Diaz as Karl Schreyer
Ron Gabriel as Ronald Nellis
Ryan Blakely as Jeremy Barton
Joey Klein as Harlan O'Brian
Julia Course as Myrtle Raylin
Brian Rhodes as Timothy Eaton
Philip Marchand as Dentist
Philip Nessel as Volunteer
Liz Gordon as Volunteer's Wife



CBC LIVE Arlene Dickinson Guest Stars on Murdoch Mysteries-0

Murdoch Mysteries Season 5
"Murdoch of the Klondike" • "Back and to the Left" • "Evil Eye of Egypt" • "War on Terror" • "Murdoch at the Opera" • "Who Killed the Electric Carriage?" • "Stroll on the Wild Side (Part 1)" • "Stroll on the Wild Side (Part 2)" • "Invention Convention" • "Staircase to Heaven" • "Murdoch in Toyland" • "Murdoch Night in Canada" • "Twentieth Century Murdoch"
Web-Series: The Murdoch Effect
Season 1Season 2Season 3Season 4Season 6Season 7Season 8Season 9Season 10