Set in Los Angeles, Death in Duplicate opens in the courtroom with the Civil trial of Samantha Q Smith, mystery author. A convicted murderer was able to bring the case against her on the basis that Smith is a co-conspirator because her book Death in Duplicate was intended to be the blueprint for him to murder his rich aunt. The convict's lawyer, who is also an Assistant District Attorney, has his own agenda and strives to have her found at fault so that he can bring a criminal charge against her.

Samantha-Sam-is contacted by Arvid, a Los Angeles Police Officer who is on partial medical leave. He is highly suspicious of why the attorney is so avid in prosecuting Sam, all based on the convict's statements. He wants to investigate and needs Sam's help.

Two of those involved in the court case are murdered. When Sam and Arvid start asking questions and finding hidden documents, more questions than answers arise.

Sam's house, which she had just purchased from the nephew of the judge who owned it, is burglarized. Someone is looking for something. Because of that Sam has her doubts about Arvid.

There are other hidden agendas and relationships related to the trial. Nothing is simple or what it seems-like sinister Russian nesting dolls.