The Xanders Case

"Janet has Doveby House, the bed and breakfast she owns with her sister, Joan, all to herself for a few weeks, and she’s enjoying the solitude. When sirens in the middle of the night wake her, however, things get complicated.
Stuart and Mary Long have lived across the road from Doveby House for years. Now their half of the semi-detached property has burned to the ground and Stuart was lucky to escape the blaze with his life.
When the police determine that the fire was started deliberately, Janet can’t help but get involved in the investigation. Having never cared for Mary, Janet immediately puts the woman at the top of her list of suspects, but the more she learns about both Mary and Stuart, the longer the list becomes."