Recently widowed and retired as a university administrator, Sally Bianco is bitten by the detective bug to clear an innocent friend of a murder charge. She travels to her hometown seeking the abused woman, only to be courted by a high school acquaintance. John Nelson, who never married.
Sally and John start an agency in Ann Arbor, Michigan. Sally's painter friend's husband dies. The chemistry professor worked on a failed drug cure. The artist's stepson links his hate-filled motives with those of an art dealer, a pawn of the dead professor's scheming boss.
Sally and her husband, John move back to St. Charles, Illinois. At their wedding reception, they are invited to the local renovated Dunham Castle. When they arrive, the father of the hostess announces his home next door has burnt down. The body found inside is not tall enough to be his wife. A crazed villain targets Sally, but it's John who pays the price.
Back in Ann Arbor, detective Sally Bianco invites a retreat participant to confide in her. The young woman had been a nurse when three patients died from their doctor's neglect. She joined the army, served in Iraq and rescued an attack dog. She's blackmailing the three doctors involved to feed a diet pill addiction. Unwilling to cease the financing of her habit, she attempts to have her dog dispatch Sally.