Burn this

From Goodreads: "Boston landlady Harriet Sutton discovers a note about a conspiracy to murder someone--and the note must have come from one of her tenants. When one of her tenants is murdered, she becomes worried when the police investigate her son, a Vietnam veteran, considering him a victim of combat fatigue who would be capable of anything. She asks forensic psychiatrist, Dr. Basil Willing, to investigate."