The citizens of Rome are enduring a heatwave and solar flares appear to be causing a series of suicides. Simona Sanna, a pathologist, is writing a thesis on real and fake suicides and, stressed by overwork, begins to hallucinate. Betty, one of Simona's neighbours, is found with a bullet in her head, having apparently taken her own life. Simona witnesses a violent confrontation between a priest named Paul, Betty's brother, and her building superintendent. When the latter also apparently commits suicide she begins to suspect the quick-tempered priest. Simona re-examines Betty's cadaver and discovers evidence that she had been forcibly drugged before her death. Becoming increasingly uneasy about her sexist boyfriend, Simona confesses that she loves Paul. The complicated trail leads to a valuable antique bible and blackmail as the motives for murder...