Having been notified that his young niece Polly is seriously ill, businessman Whitney "Cam" Cameron (Joseph Cotten) rushes to the hospital where she's being treated and is relieved when he's told that she seems to be making a successful recovery - but he's troubled by the fact that her doctor is unable to make a definite diagnosis of what went wrong. He visits with his widowed sister-in-law Lynne (Jean Peters) at her home where he gets reacquainted with his young nephew Doug (Freddy Ridgeway). Doug (who is actually Lynne's stepson) is upset about his sister's suffering, especially because she'd kept saying "don't touch my feet" and his father, Bill, uttered these same words before dying of a similar mystery illness. Cam is shocked and becomes suspicious when Polly suffers a sudden relapse and dies. Later, Cam goes to visit his old friend and family lawyer, Fred Sargent (Gary Merrill) and his wife Maggie (Catherine McLeod). During one of their conversations, Maggie remarks that from her research as a writer for the "pulps", Polly's symptoms were similar to those suffered by people who'd been poisoned with strychnine and as Cam's brother Bill had died in similar circumstances, this possibility should be considered. Cam and Fred initially laugh off Maggie's observation, but then Fred (in a later conversation) adds that under the terms of Bill's will, Lynne would only be able to inherit his estate if both his children had died before receiving their inheritances. Maggie also then remarks that her research had shown that most cases of killing by poison never actually lead to a conviction. This information along with the results of an autopsy carried out on Polly's body make Cam very suspicious of Lynne's role in Bill and Polly's deaths and extremely anxious about the welfare of his nephew, Doug. His concerns are then heightened further when Lynne announces that she intends to take Doug on a trip to Europe for about a year. Without giving them any indications of his intentions, Cam simply turns up on the ocean liner which is taking Lynne and Doug to Europe and carries out an elaborate plan to discover whether or not his suspicions about Lynne and his concern for Doug are indeed justified...

Despite its modest budget, straightforward plot and relatively short running time, "A Blueprint For Murder" is a superb and sophisticated murder mystery. Joseph Cotten is in peak form as the lead man, Whitney Cameron, who is called to the bedside of his young niece, who is dying in hospital. The child dies of mysterious convulsions, enigmatically and inexplicably crying out: 'Don't touch my feet!' The plot thickens from there, and the strange cry is discovered to have a meaning after all. This is a first rate early fifties noir with Cotton, Jean Peters as his sister-in-law, and Gary Merrill as his lawyer friend. Suspense and intrigue aplenty here, especially because pieces of information emerge at different times that throw doubt on Lynne's guilt. It is excellently directed by Andrew Stone and should be better known than it is. The story is cleverly developed, and the mystery lasts up until the very end of the film. The question is: who poisoned the niece with strychnine, and why? And who will be next? Cotton is urbane, reassuring, and very solid in the main role. Jean Peters is rather more arch than usual, with a character portrayal which is intentionally ambivalent, just to keep us all guessing. One does not know whether she is a femme fatale or not, and the whole point is that no one knows, even within the story. This is a most ingenious whodunit which will not disappoint any viewer.