Before Robert Bloch ever conceived of The Psychopath, Patrick Wymark and Margaret Johnston worked together at the Shakespeare Memorial Theatre (what would later become the Royal Shakespeare Company).
In 1956, Australian actress Margaret Johnston joined the company under Anthony Quayle. She won critical acclaim for her bespectacled, jokey Portia in The Merchant of Venice opposite Emlyn Williams as Shylock. Patrick Gibbs of The Daily Telegraph remarked on her "gay, girlish figure, with a personality all her own." Ivor Brown of The Observer complimented her performance in the trial scene, "with a playful assumption of the learned legalist" keeping a smile beneath her spectacles.
Johnston earned praise as Desdemona opposite Harry Andrews' Othello, for her "refreshingly independent air of femininity." She also won admirers in Anthony Quayle's final production for the Shakespeare Memorial Theatre. As Isabella in Measure for Measure, Johnston was acclaimed for the captivating sincerity of her playing opposite Emlyn Williams as Antonio and Anthony Nicholls as the Duke.
Patrick Wymark also appeared in Measure for Measure once again playing the comic role - this time as Pompey, the pimp who is arrested and imprisoned but is offered his freedom if he will help the overworked Executioner.
Ironically, the themes of Measure for Measure are similar to those of The Psychopath - deception, disguise, injustice and abuse of power, although Wymark and Johnston would play very different roles in the movie.