The theater lights blink, and the audience takes their seats. Reed Asylum enters the stage followed by Cin Fin-Lathen, costumed as Carmen. Cin is performing in a gala concert benefiting the Palm Beach Opera. The floorboards beneath her feet radiate with the spirits of long-gone sopranos and baritones. The opera audience is captivated by the spectacle before them. Cin as Carmen is being conducted by Kyle, a handsome, young, volatile genius. He only has eyes for her, but Cin isn't interested.

Unbeknownst to Cin, she has been lured into the tragedy and comedy that is opera. She has attracted unwanted attention and is attacked and left for dead. After this traumatic event, she slips away from herself. Cin now depends on a protective inner personality, Bella, a diva who brings with her risky behavior. Cin is so changed that her family no longer recognizes the person she has become. Harry, however, refuses to give up on her.

Unforgiveable Cin: An Opera in Three Acts is a mystery within an opera. The characters' actions are heightened as are those in many operas. This novel follows Book Four but isn't the type of mystery that readers may be used to. Tragedy, comedy, seduction, and beautiful clothes emphasize the different world Cin Fin-Lathen and Harry O'Rourke have found themselves in. Put reality aside and enter Cin's world as she tries to save herself while finding out who killed her in the first place.