As the title implies, the story is about a lover's triangle -- or rather quadrangle as we will learn by the midpoint. Despite what the title says there are actually three men vying for a woman’s attention. Daisy Walkern, a vapid femme fatale concerned with only herself and sexual conquests, is rescued from her life as single mother by Alan Walkern, the gallant but very homely and disabled (he has a club foot) physician. He marries Daisy and becomes stepfather to her unruly child Barney. While married to Alan, Daisy becomes pregnant and they eventually have a second son, Peter. But while married to Walkern Daisy continues her life of teasing and taunting any man who will pay attention to her.
When the book opens Alan Walkern is dead. And one of Daisy's "lovers" is dead, apparently a suicide by gun. Paul Lathbury is found in the hayloft of a barn shot dead. But the gun is nowhere to be found. How then can the death be a suicide? Did someone remove the gun to prevent anyone thinking the handsome, well-liked, highly successful man killed himself? Another young doctor, Alastair Southery, is assigned as a locum tenens to fill in for Dr. Walkern until a new physician can be hired. Alastair begins an innocuous investigation with only a few questions concerning Paul's death. But the most senior physician in town, Dr. Forty, an associate of Dr. Lathbury and Dr. Walkern is not satisfied with the police work. He is also concerned about an odd coincidence. Dr. Walkern supposedly died from aplastic anemia and Dr. Lathbury whom Alastair is working for, is currently being treated for the same condition. How is it that both of the town's doctor's contracted anemia within months of each other when prior to that both men had no signs of any chronic illness? Dr. Forty is relentless in pursuing this medical coincidence. He even suggests that Walkern's death and Paul Lathbury's death are related because they were linked to Daisy Walkern.
Though he at first dismisses Dr Forty's wild speculation that someone is killing men who cross Daisy -- could it be Daisy herself? -- Alastair finds himself cast into the role of a medical detective. He begins subtly questioning everyone in the village, eventually spying on them and doing a little snooping into their homes and personal belongings. When a medicine bottle turns up missing he begins to think that Dr. Forty's theories may have some truth in them. Alastair discovers that what can cure illness can also induce illness and he is determined to expose the murderer and prevent more deaths.Some of the supporting characters provide welcome relief in a story fraught with tension and danger. Alastair befriends a seven year boy, the son of a talented portrait painter Calliope Eldernell who earns her primary income as a servant in the Lathbury home. Both Calliope and her son Tim serve as the common sense characters who seem to be Alastair's only friends and provide the groundwork for what ultimately is a happy ending for this trio. Tim is a delight and Calliope, a troubled woman who doubts her own artistic talent, provides hope in a book that is largely doom-laden and focused on the darkness within everyone else in the village.
Fleming's first crime novel is utterly fascinating. She has created both a medical detective novel and a horror novel simultaneously. The murder method turns out to be diabolical. It's a modus operandi first introduced as a fictional murder method back in the late 19th century by a handful of astute short story writers like L. T. Meade, but not truly explored by 20th century crime writers until the WW2 era. A master of innovation in the crime novel Fleming has never been noted to follow genre formula. She often employs imaginative twists and trenchant satiric touches both of which are on display in this first novel that promised so much. Many of her later novels are superior and this first effort definitely predicted great things for her. It’s a shame so few people know of her work and that 95% of her crime novels are out of print.