Sarah pursues Helena, who is being held in a compound far away; Sarah must deter a Topside investigator.
Castor pursues the clones in order to obtain original tissue samples; Helena is examined by a new villain.
Helena takes shelter behind enemy lines, and Sarah and Art struggle to protect her and end the siege.
Paul learns the truth about Coady's plans for Castor and has no choice but to make a dangerous play; Alison and Donnie hatch a plot of their own regarding Bubbles.
Leda and Castor hunt for the original clone DNA; Mark and Gracie pursue new leads; Art and Sarah reunite.
