Secret House of Death — Ruth Rendell

Louise North doesn't care what the neighbors think. She lets her lover leave his car just outside her house in broad daylight, telling everyone a cockamamie story about him being a central heating salesman. Still, it's a shock when she's found shot dead, covered by the equally dead body of the "salesman." Now Susan Townsend -- the Norths' next-door neighbor, who discovers the bodies -- must help Louise's husband, Bob, get back on his feet. But is she helping a neighbor . . . or a murderer?