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"I Know What You Did Last Autumn" is the sixth episode of the fifteenth season of Murdoch Mysteries and the two hundred twenty-first episode of the series (not including the three stand-alone holiday specials). It first aired on October 25, 2021.

WARNING: Anyone who is disturbed by clowns is strongly advised to skip this episode.


At Halloween, old rumors of a clown terrorizing high school students become reality when young Irene Robbins is stabbed to death in front of her sweetheart Perry Balfour. Murdoch interviews the survivor, but his story does not align with Mrs. Hart's autopsy results. Then a short time later, the clown kills again.

Character Revelations

  • Watts and several other lads at the Station House compete in a pumpkin carving contest revealing he is much better as a detective than a jack o’ lantern maker.
  • On the other hand, Mrs. Hart is rather skillful with a knife outside the City Morgue.
  • Mrs. B roasts pumpkin seeds and had accidentally dropped pumpkin pie spices on a batch which George likes better than the fibrous plain ones.


  • Assisting in the investigation is persistent Miss Cherry who had written an article on a clown stalking 'teeners' – "slang for youth in their teenage years" – the previous Halloween.
  • George Crabtree creates pumpkin spice coffee.

Historical References

  • This episode takes place in Toronto 1908 – Edward VII (Albert Edward;1841-1910) is King of the United Kingdom of Great Britain and Ireland and of the British Dominions beyond the Seas.
  • The practice of decorating jack-o'-lanterns originated in Ireland (where large turnips and potatoes served as early canvasses), from an Irish folktale about a man named Stingy Jack. Irish immigrants brought the tradition to North America, home of the pumpkin, and it became an integral part of Halloween festivities.
  • A high school in Toronto, Ontario, Canada, Jarvis Collegiate was founded as a private school in 1797. In 1807 the government of Ontario, then known as the British colony of Upper Canada, took over the school and incorporated it in a network of eight new, public grammar schools (secondary schools), one for each of the eight districts of Upper Canada. After various name changes from Toronto High School to Jarvis Street High School along with a new building at 361 Jarvis Street, the school was given its current name, Jarvis Collegiate Institute, in 1890.


  • There is a musical twist to Robert Carli’s Opening theme, as it was for the stand-alone Halloween treat Sir. Sir? Sir!!! in Season 12; The other Halloween timed episode was in Season 13 with Murdoch and the Cursed Caves, but none in Season 14.
  • While not the first episode to have a dead body within minutes of the show's opening, this one has eight victims with 5 dead bodies by the end of the episode (also see body count at City Morgue).
  • This episode takes place on the Halloween weekend and the Monday after; Halloween fell on Sunday, October 31, 1909.
  • Like previous Halloween episode(s) this is an homage to classic horror movies (i.e. Scream, It, Halloween, Telefone, Psycho), either one loves it or hates it - there is no in-between for Murdochians; This one is a deep nod to the 1997 American slasher I Know What You Did Last Summer which was remade (and updated) into a TV series of the same name in 2021.
  • Julia Ogden's costumes are reminiscent of the Wizard of Oz and Brigadoon.
  • Prop Master Craig Grant took a paintball mask that he "covered in papier maché and mouldable plastic to get the desired features. Then, it was vacuformed to make multiple copies".
  • The clown's "creepy shoes" were made by Adam Smith, costume department member, live tweeted Joanna Syrokomla, who tried "the prototype the moment they arrived. I could only side shimmy in them as walking forward, let alone chasing was difficult".

Notable Quotes

Crabtree to Brackenreid: "When you're done with an apple, you wouldn't roast the seeds and eat them."


Main Cast

Yannick Bisson as Detective William Murdoch
Hélène Joy as Dr. Julia Ogden
Thomas Craig as Inspector Thomas Brackenreid
Jonny Harris as Constable George Crabtree

Recurring Cast

Daniel Maslany as Detective Watts
Shanice Banton as Violet Hart
Lachlan Murdoch as Constable Henry Higgins
Bea Santos as Louise Cherry

Guest Cast

Lucy Ellis as Irene Robbins
Lyla Porter-Follows as Leigh Iverson
Michael Therriault as Roger Douglas
Ben Caldwell as Perry Balfour
Mika Amonsen as Donovan Kent
Ellie O'Brien as Andrea Porter
Jamie Lauren as Heather Iverson

Non-Credited Cast

Paul Irving as Constable Paul


Murdoch Mysteries Season 15
The Things We Do for Love Part 1The Things We Do for Love Part 2ManhuntBlood on the TracksLove or MoneyI Know What You Did Last AutumnThe Incorrigible Dr. OgdenMurdoch Knows BestThe Lady VanishesDrawn in BloodThe Night Before ChristmasThere's Something About MaryMurdoch on the CouchThe Witches of East YorkRawhide RalphIt's a Wonderful GameBloodlinesPatriot GamesBrother Can You Spare a CrimePendrick's Planetary ParlourDevil MusicSweet AmeliaPay the PiperClose Encounters

Season 1Season 2Season 3Season 4Season 5Season 6Season 7Season 8Season 9Season 10
Season 11Season 12Season 13Season 14