Jonathan Hackett plays Rev Jim Hale in this episode. He previously played the role of Reverend Thorne in episode 4.4, Who Killed Cock Robin? (2001).
There is a character in this episode called Margaret Hopkins and Sergeant Dan Scott is played by John Hopkins. In the 17th century the infamous 'Witchfinder General' was Matthew Hopkins.
It's not clear if it's a good or irony but Malpas says "there will always be people who prefer aspirin to willow bark." Aspirin was derived from willow bark, which contains the active ingredient salicin. That was then refined into acetylsalicylic acid, or aspirin.
Maggie O'Neill plays Agnes Waterhouse in this episode. She returns in episode 19.6, The Curse of the Ninth (2017), in the role of Audrey Glenhill.
Keith Barron (Alan Clifford) and Maggie O Neill (Agnes Waterhouse) previously starred together in the 1989 BBC drama " Take Me Home".