In a twisted manner of self-styled justice, a vigilante known as 'Doctor Rx' has been killing acquitted criminals.

Strangling his victims - and then leaving a gruesome calling card with only the letters "Rx" scrawled on it - the identity of the avenger has baffled the police and mystified investigators.

Against the wishes of his new wife Kit (Gwynne), private detective Jerry Church (Knowles) is brought on to the case, in hopes of unmasking the elusive Doctor before more murders are committed.

But will the fiendish Rx prove too clever for them all? Is there more at play here than just the diabolical schemes of a madman?

Unfortunately, Doctor Rx is a misfire on nearly all fronts. Individually, Knowles and Gwynne deliver okay performances, but together they lack sufficient chemistry to ignite any fire under the film's hohum mechanics and lazy scripting.

Worse still, we're forced to endure some heavyhanded attempts at comedy - courtesy of Church's butler Moreland - precious time that would've been better spent creating story tension or suspense.

But most egregious is the complete and utter waste of the great character actor Lionel Atwill.

His supporting role here is relegated to no more than a few minutes onscreen, symbolizing the misplaced priorities and futile ploddings of Doctor Rx.