Joanna (Christina Nagy) has been paralysed from the waist down ever since she was a young girl and a crazed priest assaulted her in broad daylight, but she remembers nothing of the incident now, as an adult. She is being courted by her fencing instructor Craig (David Warbeck) who is nothing but encouraging towards her, helping her enter competitions with her archery skill and very much in love with her; the feelings are reciprocated, but is she ready to marry him? Her best friend and care assistant Ruth (Carroll Blumenberg) is not so sure, but that might be because she has designs on Joanna herself, though the disabled woman is more worried her attacker may have returned...
Formula for Murder, or 7, Hyden Park: la casa maledetta as it was called in its native Italy, was the final film directed by Alberto De Martino after a healthy career in mostly derivative but often amusingly crafted movies usually found on the lower halves of double bills. Perhaps for that reason this last effort looked less like it belonged in the eighties and more like it was some lost film from the seventies that had been locked in a vault somewhere and rediscovered circa 1985 to be released to an indifferent public. Not that it was a bad movie, it's just that giallo works were getting to be pretty old hat in spite of the genre still struggling on in the face of other films in the country's output.
But there were only so many Alien, Terminator, Rambo and Mad Max copies that the industry could produce, so it was cheering to see something that bit more faithful to the style which supported it for so long. However, just as the sword and sandal mini epics fell by the wayside after the sixties probably thanks to the sheer weight of them flooding the market, giallo was suffering this decade and De Martino's would-be swan song was not going to change that as unless you were an addict of these things, there was little to inspire aside from the ever-reliable presence of David Warbeck whose nicer than nice character was instrumental in the twist which showed up half an hour in and descended the plot into Wait Until Dark territory.
Not that Joanna is blind, but she is disabled, and that puts her at a disadvantage when someone is out to get her and, for example, her wheelchair has a habit of locking up (although the eagle-eyed might spot actress Nagy moving her legs rather more than was possible for a paralysed individual). This meant she keeps having visions of her priest attacker holding a bloody doll advancing on her - ah, but are they visions at all, or is there really someone there who nobody else manages to see? The answer to that will surprise nobody, not even those who have never so much as seen a giallo before, so what you were left with was a lact act campaign of terror against the hapless Joanna either in an effort to terrify her to death or actually use a sharp instrument instead.
Putting the lead character at a disadvantage is a common enough trope in thrillers, though physical disadvantages are not quite as common, yet they did exist such as Dorothy Maguire in The Spiral Staircase or Susan Strasberg in Taste of Fear, both works which giallo would owe something to in general if not strictly specifically. Here De Martino overdid it somewhat, really piling on the drawbacks so we got such silliness as the possibility that Joanna could die during sex after getting too worked up, and throwing a killer of priests into the mix: the first scene after the flashback to her childhood trauma is one such man of the cloth being hacked to death in the confession booth, though precisely why this is happening is not something the script went into in great detail other than to establish the villain as a kill-happy psychopath. In the main, the director kept the action coming with efficiency if not eclipsing the essential daftness of his own screenplay (penned with Vincenzo Mannino); nobody was going to mistake it for a classic of the form, but it did have a giddy energy. Music by Francesco De Masi.