[4] In 1860, Edward Styles is accused of being the notorious Haymarket Strangler, who brutally killed five women by partially strangling them with one hand before stabbing them to death.

Twenty years later, James Rankin, a novelist and social reformer, launches a private investigation to prove that Styles was innocent and would not have been convicted if adequate legal representation had been provided for him at trial.

Rankin takes possession of Tennant's abandoned personal effects, which include a journal containing unusually detailed descriptions of the Strangler's victims and a surgeon's kit with a missing knife.

At the Judas Hole, Rankin gleans from Cora that she never saw the Strangler's face, and that Tennant was a regular patron who made unwanted advances towards Martha Stuart.

Rankin deduces that Tennant was the real Haymarket Strangler, and suspects that his breakdown was precipitated by him disposing of his knife, the symbol of his homicidal compulsion, in Styles' coffin in a lucid moment when he was overwhelmed by guilt.

Finding the knife amid the bones, he takes hold of it and undergoes a transformation that contorts his face, paralyzes his left arm, and alters his personality.

[5] Executive producer Richard Gordon and interviewer Tom Weaver talk about the making of The Haunted Strangler on the audio commentary of the Criterion DVD, available as part of the 2007 box set Monsters and Madmen.

[2] The Monthly Film Bulletin wrote: "This ludicrously improbable plot, which peters out into a series of tediously repetitive chases, is used as an excuse for the now familiar ingredients of the current horror trend.