The Affairs of Others by Amy Grace Loyd

Celia Cassill, who lost her young husband five years ago, is the owner of a small apartment building. She is determined to live a life at a remove from the chaos and competition of modern life. But everything changes with the arrival of a new tenant, Hope, who is on the run from her husband’s recent betrayal. When Hope begins a torrid and noisy affair, and another tenant mysteriously disappears, the carefully constructed walls of Celia’s world are soon tested and the sanctity of her building is shattered.