When Cosima admits doubts about finding a cure in time to save her life, Sarah makes a lone decision that exposes Kendall to those she’s spent years hiding from. Meanwhile, Art and Felix team up to protect naïve clone, Krystal Godderitch, from herself.

Paul digs and finds the ugly truth behind the Castor Boys’ logbooks of names, pushing him into action. Meanwhile, Felix is desperate for info on Sarah’s whereabouts, and presses the still-ailing Rachel for any shred of a lead. In order for Donnie and Alison to take their money-making endeavor to the “next level” she must introduce Jason Kellerman to her unique business plan.

With Helena forced to take shelter behind enemy lines, it’s a bloody last stand for survival as Sarah and Art struggle to protect her, and end the siege on the sestras once and for all.

Castor and Topside force Sarah to make uneasy alliances. But there is some rest for the wicked, when Donnie gives Helena an unexpected ‘gift’, and the results of Alison’s candidacy finally come in. Even as team Leda takes a moment to breathe, change is afoot and a life hangs in the balance.

Mrs. S orders the sisters to take a night off from sleuthing to celebrate Felix's art opening. But while Felix attempts to impress a famous gallerist with the help of his sestras, Sarah remains on edge with a nagging suspicion that S is hiding something. Meanwhile, wounded and desperate, Rachel reunites with an old ally, but their plans for revenge on Neolution put Clone Club in the line of fire.

Sarah’s last chance to bring her nemesis back to sanity slips away as Art intervenes to get answers of his own. Meanwhile, the Orphans must decide whether to make peace with their creators, as Sarah is forced into a deadly confrontation with their enemy.

As P. T. Westmorland demands a more aggressive action on Kira, and Sarah fights to save her daughter, Rachel discovers a dark secret that makes her question her place within Neolution. Meanwhile, Cosima has returned with a vital clue to Westmorland's true identity.

A devastating loss is eclipsed when word reaches Sarah that Helena has been kidnapped. Clone Club bands together in a race against time, determined to find her before she has her babies. And with time running out, Sarah is forced into action in a last-ditch effort to save her sestra.

After two months of respite, Sarah’s hard-won refuge in Iceland is shattered by a Neolution attack. Once again forced to flee, she realizes no matter how far her family runs it will never be far enough.

When communication with Cosima is cut off and Neolution appears to be within striking distance, Sarah's alliance with Rachel goes out the window. Sarah lures a high-level Neolutionist into a trap, and sets out to bring down Neolution once and for all.

After Kira’s life is threatened, Sarah is on the warpath, but Dr. Leekie makes her think twice about her plans for revenge. Meanwhile, Cosima faces the truth about Delphine, forcing her to choose sides. Now, it’s up to Sarah to decide the killer’s fate, but the truth about where Sarah came from changes everything.

When Rachel makes a promise to Sarah, it comes with a hefty price. Meanwhile, Helena and Gracie work with the Hendrixes, and Donnie takes Kellerman to task. Over at Castor, Coady and Benchman scheme to track down the Castor Original, and Rudy descends on DYAD for a much needed asset.

Sarah, Felix, and Mrs. S are in London to track down the Castor Original, but their enemies are not far behind.

With Susan Duncan deposed, Sarah finds herself in the same position as Rachel — under the heel of a new HBIC — causing the archenemies to come together for the greater good. Cosima and Susan butt heads on the ethical implications of human experiments. Meanwhile, when the Hendrixes' legal counsel, Adele, further investigates Donnie’s case, she begins to suspect Felix is keeping deep secrets. Helena’s arrival forces Felix to make a difficult decision.

Sarah’s hunt for answers is interrupted by a trip to the suburbs. Alison’s paranoia has boiled over, putting all the Orphans at risk. But when Sarah, Alison and Beth’s worlds dangerously collide, Sarah must decide who to trust with her secret.

Sarah's actions pit the Orphans against each other as she tries to plan her next move. As Paul tries desperately to cover up Sarah’s existence, Alison takes vengeance on her suspected monitor, which could cost her everything she holds dear.

Alison must secure a store front in order to take her and Donnie’s business to the “next level”. But things don’t go according to plan when her mother, Connie, proves to be a major hindrance. Cosima is facing familiar health issues and calls upon beleaguered Alison for a favor. But with Alison working to save an imperiled Donnie from the merciless hands of a drug lord, it’s Cosima who ends up doing a favor. An unassuming Scott gets closer to the greatest discovery of all, when he sits down with beleaguered clone Rachel.

After evading a Neolution attack in Iceland, Sarah returns home to track down an elusive new ally. As Cosima struggles with Delphine’s disappearance, Alison and Donnie host a pregnant and ever-hungry Helena. Meanwhile Felix, feeling like an outsider, embarks on his own journey of self-discovery.

Sarah’s day off to reconnect with Kira quickly turns into a sleuthing mission aimed squarely at discrediting Felix’s new ties. Cosima steps up with Donnie to further investigate the Neolutionist fertility research center. While Donnie bumps into an all too familiar face, Cosima makes a shocking discovery that leads her into a dangerous encounter.

As Alison is terrified by Neolution threats made against Donnie, Sarah and Mrs. S question her loyalty to her sisters. While Sarah is distracted, Siobhan sneaks out to seek vengeance. Meanwhile, Cosima and Susan Duncan work together in a final attempt to discover a cure.

Sarah realizes that the Orphans’ survival is going to take more than police work. But tracking the killer threatens Sarah’s long awaited reunion with her daughter, Kira. As Sarah gets closer to the killer, the killer gets closer to the truth – the ensuing showdown threatens to expose her ruse as a cop.

When terrifying evidence suggests the Orphans are part of a sinister ongoing experiment, Sarah’s suspicions turn to Paul, Beth’s boyfriend. But her probing inadvertently triggers Paul’s own investigation, bringing him dangerously close to the truth. Meanwhile, paranoid Alison piles on a whole new level of complication.

Helena and Sarah are reunited at the Castor camp. As Sarah suffers testing, Paul appears to chide her; but his allegiances are beginning to strain. While the Leda family worries about Sarah’s absence, Gracie ‘breaks loose’ under the care of Mrs. S and an unwilling Felix. Cosima falls hard for an internet date, Shay.

Cosima is forced into an alliance when an old enemy returns to the island, accelerating P. T. Westmorland's sinister agenda. Meanwhile, on the mainland, Krystal stumbles onto a vital clue to the Neolution endgame. Sarah and Mrs. S’s research into Neolution's corporate ties leads to the cosmetics industry and an inevitable cross with Krystal Goderitch. But before Sarah can dig deeper, Krystal hijacks the investigation.

Sarah, a streetwise hustler on the run from a lifetime of bad decisions, witnesses the suicide of a stranger who looks just like her. Sarah assumes her identity, hoping that cleaning out the dead woman’s bank account will solve all of her problems. Instead, the street smart chameleon is thrust headlong into a kaleidoscopic mystery. After taking on the new identity, Sarah quickly finds herself caught in the middle of a deadly conspiracy and must race to find answers.