While Harvey and Mike have unpleasant work to do for one of their biggest clients, Louis faces a huge challenge and Rachel tries to collect on an old debt.
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.
Rachel bargains for her freedom with decoding Duncan's Moreau book; Sarah must pursue the Original Castor.
Clone Club heads to London to track down the Castor Original, but their enemies are not too far behind.
When a disturbed man takes a woman hostage outside an office building, the SRU is quick to respond to save the innocent hostage and bystanders caught in the crossfire.