A man buys a synthetic human, or synth, to help around the house and try to save his marriage -- unaware that "Anita" has a history of her own. While a young man attempts to reunite his separated synth friends, a retired engineer faces the reality that the synth he thinks of as a son may be irreparable.
George is assigned an oppressive new synth to be his caretaker, and Leo is injured while retrieving intel about Mia. Laura is preoccupied with her suspicions of the family's new synth, Anita, and inside the brothel Niska lashes out after meeting a John with whom she cannot comply.
Detectives Drummond and Voss search for Niska, who rebuffs her friends and intends to live on her own terms. Laura is forced to reconsider returning Anita after she saves Toby's life, and George escapes from Vera and takes Odi on the road.
The Hawkins take Anita for testing and discover that she is much older than they believed, while their daughter Mattie arranges a meeting with Leo and Max -- who are desperate for a lead on their missing friend. Detective Drummond takes matters into his own hands after being suspended from duty and kicked out by his wife, and Niska finds herself inside a synth "smash club."
Leo convinces Niska to lay low at Dr. Millican's house while he tries to recover Fred and Mia -- only to have news of the "Killer Synth" leak to the media. While Karen investigates the incident at the smash club, Mattie flees with Anita after her parents decide to have her recycled -- bringing her to Leo, who hopes he can recover her buried personality.
With the family in tatters Laura comes clean to her daughter about her secret past -- which leads to Mia's consciousness resurfacing in Anita. Karen inches closer to Niska, and Leo discovers that his lost brother is alive.
Karen confronts Niska at George's home, revealing her shocking connection to Leo's family of synths. Meanwhile the Hawkins offer the synths a safe haven, where Leo hopes to save Fred's life after his body is recovered.
The fugitive synths are held prisoner in Hobb's facility, as he tries to extract the secrets of creating living artificial intelligence that have been programmed into their brains. However, he discovers a vital piece of the puzzle is still missing -- and not even Leo knows where it can be found. Laura and her devastated family come to realise how much Mia means to them, and resolve to rescue her and her friends from a life of captivity. (Radio Times)
