Rather then trusting her witness protection program handler, FBI Agent Victor Machado, sole gangster murder trial witness Bridget Kelly make a run for it on her own, before the trial. She's welcomed in New York by her rich, identical twin sister Siobhan Martin and her dream husband Andrew. Only a suicide note on their yacht informs Bridget that spoiled-rotten Siobhan wasn't happy, but she accepts taking her place as seemingly perfect cover. Shortly after she discovers her twin wasn't faithful either, the whole family is a mess, notably drug-addicted daughter Juliet. ...
FBI Agent Machado tries tenaciously to properly question 'Siobhan', who dodges him as zealously. That game is up when she must organize in one day, with a brilliant gay event planner, a party fro Henry and his partner Olivia's investment firm, and he already decided on the loft where she left the assailant's corpse, which she's now unable to evacuate and must hide. Henry is delighted with the 'old Siobhan' who cares again for him and 'their rebellious junk daughter, not unlike young Bridget. Henry still dodges Gemma's suspicion of adultery and asks 'Siobhan' why they ...
Henry grudgingly agrees to let Andrew withdraw his investment in his hedge fund, which his firm partner sees as crucial foothold to lure wife Gemma's family fortune. Based solely on a photograph used by her assailant, Bridget speculates that Henry might have order a hit-man for Siobhan, whose former utterings she now reads in that light. FBI Agent Machado is increasingly openly vexed by "Siobhan's" lack of cooperation, while the real one, learning about her closed Manhattan accounts, turns even more grimly on her 'insufferable' twin.
Still posing as Siobhan, Bridget, and Andrew head to the Hamptons with Gemma and Henry to celebrate her birthday. Despite the close quarters, Henry is dead-set on rekindling his affair with Siobhan. Gemma learns some unsettling news, while FBI agent Victor Machado closes in on some new information, which forces Bridget to reveal some of her past in order to protect her secrets.
Henry worries more about his failing novel ambition then his dysfunctional marriage. That only strengthens cheated Gemma's resolve to clean him out in a divorce, so she blackmails 'Siobhan' to provide irrefutable proof in bed, even after being informed of the twin sisters switch, yet a reconciliation is attempted beyond Gemma's midnight deadline. Andrew greatly appreciates "Siobhan's" help with stepdaughter Juliet, who is spared rehab but transferred to a public school and turns on 'Siobhan'. The mobsters torture Malcolm to put them on Bridget's trail.
Henry worries seriously as blood traces suggest his ex Gemma may be murdered, he disappearance puzzles Bridget as much. Andrew's daughter Juliet thought to get an easy start with clean slate at her new high-school, but is targeted by a haughty bully and the principal informally got her crushing record, yet young teacher carpenter sides with her. Gangsters finally break private eye Malcolm by torture to lead them to Siobhan. Forensic courtesy finally brigs agent Machado on the trace of the sisters' twin link.
Henry worries about his ex Gemma's whereabouts, and being the police's prime suspect. Agent Machado's progressing investigation forces Bridget to admit to shocked Andrew and Henry she's a twin, not being Siobhan's sister. She's delighted with private eye Charlie Young offering his 'cleaner' service to cover her tracks, notably an abandoned car, but he has a secret agenda and secret real master. To Andrew's bitter dismay, junkie daughter Juliet gets in big trouble again by joining her new school's party scene, so he suspends her trust fund allowance as desperate last ...
Andrew and Bridget are told some upsetting news that also affects Henry. Juliet continues to form an unlikely bond with her teacher Mr. Carpenter and Malcolm shows up in New York, where Agent Machado confronts him. Meanwhile, Siobhan's relationship with Tyler is jeopardized.
Bridget begins to realize she is developing feelings for Andrew, while Henry and Andrew's business partner Olivia bond over common interests. Malcolm is suspicious of Bridget's new NA sponsor Charlie and Bridget makes an appointment with Siobhan's therapist, hoping it will help her discover some insight into her sister's life.
Henry begins to target someone as a suspect in the disappearance of his wife Gemma and realizes he must work with Bridget to find out more information. Malcolm talks to the police about his suspicion of Charlie, while Juliet develops an unhealthy obsession with her teacher Mr. Carpenter. Meanwhile, Agent Machado meets with an informant back in Wyoming.