Like the butterfly effect — the theory that the flapping of a butterfly's wings can affect the weather a continent away — one seemingly insignificant event sets the suspense in motion in Rachel Joyce's haunting second novel.

As she did in her 2012 debut novel, "The Unlikely Pilgrimage of Harold Fry," which was long-listed for the Man Booker Prize, Joyce flings "Perfect's" characters into chaotic situations fraught with misgivings and confusion.

The pivotal event in "Perfect" is inspired innocently enough by a boy's love for his mother and his determination to always do what's right. Byron Hemmings is a thoughtful, intelligent 11-year-old fascinated by life's minutiae. When his school chum James tells him that 1972, the year in which the story is set, is a leap year, he becomes obsessed with the fact that scientists are adding two seconds to the year because "time was out of joint with the movement of the earth."

To Byron, two seconds is the difference between "something happening and something not happening" and, sadly, those two seconds will forever change his life. As Joyce writes, "the repercussions were felt for years and years."

On what starts out to be a normal day, Byron's mother, Diana, is driving him and his sister, Lucy, to school when Byron believes his watch has jumped ahead two seconds. He distracts Diana with the alarming news, then witnesses an accident that neither Diana nor Lucy see. Should Byron tell Diana what he thinks he saw? If she believes him, what steps should she take to make amends? Doing the right thing seems logical, but in the world Joyce creates it's not that simple.

Byron sets the story's chaos in motion — and the plot points are surprising — but Diana is the novel's most haunting and memorable character. Her innate honesty, when she hears about the accident, gives way to remorse and guilt. Those feelings, in turn, make her vulnerable to the emotional blackmail initiated by Beverley, her bizarre new friend. In the tradition of the beautiful and fragile blondes who populate Alfred Hitchcock's films of suspense, the lovely, fair-haired Diana is soon living a nightmare from which there seems to be no escape.

Diana's descent into terror is provocative enough to carry this story, but Joyce complements it with a contemporary one about an equally fragile man named Jim who has spent most of his life in a facility for the mentally ill. His connection to Diana will surprise many readers as Joyce spins this equally compelling subplot toward its shocking revelations and conclusion.

Carol Memmott's book reviews also appear in the Chicago Tribune and People.