After Ettie Smith's friend, Agatha, dies, Ettie is surprised to find that Agatha has left her a house. During building repairs, the body of an Amish man who disappeared forty years earlier is discovered under the floorboards. When it comes to light that Agatha and the deceased man were once engaged to marry, the police declare Agatha as the murderer. Ettie sets out to prove otherwise. Soon Ettie hears rumours of stolen diamonds, rival criminal gangs, and a supposed witness to the true murderer's confession. When Ettie discovers a key, she is certain it holds the answers she is looking for. Will the detective listen to Ettie's theories when he sees that the key belongs to a safe deposit box?