Burn This — Helen McCloy

Boston landlady Harriet Sutton discovers a note about a conspiracy to murder someone - a note that must have come from one of her tenants. When a tenant is murdered, she asks psychiatrist-sleuth Dr Basil Willing to investigate. Her son, a Vietnam veteran whom the police consider a victim of combat fatigue who may be capable of anything, is under suspicion. And as the mystery unfolds, Harriet Sutton tries desperately to prove them wrong.