The Beast Within[5] is the upcoming eighteenth episode of the third season of Shadowhunters: The Mortal Instruments.



  • This was written as a Halloween episode.[2][3][8] It was set to air in October 2018 as part of Freeform's "31 Nights of Halloween" programming,[9][10] before 3B was pushed back to 2019.
  • Filming ran from March 29 to April 14, 2018,[11][8][12][13] with supposedly only eight work days in total during that time.[12]
  • Show writer Bryan Q. Miller used the words "the trick" to tease the episode, suggesting that a trick may be involved in this episode.[14]