A streetwise young woman sees a way out of her problems after witnessing the suicide of a woman who looks exactly like her. Sarah takes over Elizabeth Childs' life, but discovers a conspiracy about her own identity -- and that she may be giving up her own life.

After Beth's partner steals her money out from under her nose, Sarah must testify in an accidental shooting case and get her badge reinstated. Meanwhile, the German leads Sarah to another twin who may hold the answers she is looking for.

While dealing with the revelation that she and her look-alikes are clones, Sarah must acclimate to Beth's police life when she is reinstated. But when the body she buried is uncovered, Sarah is haunted by the murderer whose identity she does not know.

Sarah hunts for one of her clones who may be a serial killer, putting at risk her long-awaited reunion with her daughter and threatening to expose her cover as a detective.

Sarah begins to suspect that she is part of an on-going experiment and is being closely monitored, and turns her suspicion on Beth's boyfriend, Paul. Alison, in turn, begins to suspect her own husband.

When Alison's suspicions about her husband erupt into full-blown paranoia on the day of her block party, Sarah comes to her aid. Meanwhile, Cosima's new friend introduces her to a charismatic scientist.

Helena approaches Sarah demanding information about the other girls, and Paul's position is compromised when his handlers learn that Beth is not Beth. Meanwhile, Cosima gets closer to Delphine and Dr. Leekie.

Beth's partner discovers the twins' existence and questions Sarah, while Delphine gets closer to Cosima and her secrets. Alison seeks personal revenge on the person she suspects is her monitor, and Helena sets her sights on Sarah's daughter.

Sarah agrees to meet with Dr. Leekie face-to-face after he learns who she is. Alison is ambushed at home, Cosima faces the truth about Delphine, and Helena's handler turns against her.

As Sarah turns to her mother for answers, she and the other orphans are offered terms of peace from their creators. Cosima hopes her genetic code holds answers to her failing health, and Helena draws Sarah into a showdown.