Identical twins Emma and Sutton, separated at birth, finally meet. Emma temporarily assumes Sutton's well-to-do life as Sutton searches for their biological mother.
Since concern for Sutton's safety seems to be occupying Emma's mind, she starts to let pieces of her own personality emerge. Although Emma is worried by her behavior, it seems her friends and family are enjoying the change in Sutton's character. Wanting to please the father she never had, Emma must learn to ballroom dance for the annual father-daughter dance. Realizing she is in dire need of assistance, Ethan offers to help, in turn risking revealing his and Sutton's secret relationship. Will Emma be able to put aside her worries for Sutton and shine on the dance floor? Or will the night's series of events force her to reveal her true identity? Meanwhile, as the teenagers do anything to keep their secrets, the parents may be lying to keep life-altering secrets of their own.
After revealing Sutton's real relationship with Ethan, the Mercers insist she invite him over for dinner. Hesitant because of his obvious feelings for Emma, Ethan obliges, only to have the dinner cut short by a disturbing visit from Dan. As Emma and Ethan struggle to keep order in Arizona, Sutton and Thayer discover shocking revelations in Los Angeles pertaining to the search for the girls' birth mother. Although the outcome may not turn out to be what Sutton had hoped for, it does lead her to wonder what everyone around her has been hiding for all these years. Will Sutton be able to find the answer about why she and Emma were separated, or will her curiosity put her and her loved ones' lives in danger? Meanwhile, Laurel falls for a new guy in school hoping she will finally have something of her own, as opposed to always being in Sutton's shadow. Unfortunately her wishful thinking is cut short when Char calls dibs on the one Laurel did not want to share.
Sutton and Emma soon find they have had the same dreams and similar childhood experiences.
Emma is forced to go up against Neesha for Homecoming queen which causes problems with her and Sutton. Sutton and Emma both try to find more info on their mom while Alec and Ted try to hide it.
Sutton is furious when she learns that Emma and Ethan kissed. Sutton and Emma continue to find more info about their mom. Meanwhile, Laurel becomes suspicious when Justin keeps breaking dates. Also, Mads learns Edwardo is moving and Char goes on a date with a boy she found in her pool.
Questions surrounding Emma arise when Thayer returns to Phoenix and everyone deals with Eduardo's accident. What does Emma know about the accident, and why does Thayer seem to know more about the situation even though he has been in L.A.? Sutton's friends are tired of the lies and demand answers from Emma. Not exactly knowing the whole story surrounding Eduardo's accident, will Emma finally tell Mads and Char about the switch to save their friendship, or will she risk it to save Sutton's secret? Meanwhile, Sutton finds more trouble than she expected at Dowinger Clinic as she finally comes face to face with her mother.
With tensions already high, Emma is thrown into a tailspin when her creepy foster brother, Travis, shows up from Las Vegas. Seeing he has an upper hand with Emma, Travis decides to use his knowledge of Emma's situation to his benefit. With her relationship with Ethan still strained, she has no one to turn to and forced to go along with Travis' plan if she has any hope of getting him to leave her alone. But with her old life looming over her, will this be the straw that breaks Emma's back? Meanwhile, Sutton is forced into Emma's life when she is sent back to Las Vegas.
Secrets abound in the Mercer household and Emma has had about enough of it. When she overhears an argument between Ted and Kristen, Emma thinks she finally can put a stop to all of the lies and get some real answers out of Sutton's mom. But does Emma really think that she could pry the truth out of a secret that has been hidden for almost seventeen years? Or will the secret Kristen has been hiding turn out to be not the biggest secret lurking around the Mercer house? Meanwhile, Sutton gets a glimpse into what Emma's life has been like when she is forced to pretend to be her sister while in Las Vegas.
On their seventeenth birthday, Emma's ideal life is about to come to an end when a vengeful Sutton makes her way back to Phoenix to get her life back.
It's been a tough night for Emma and Ethan, and things are about to get tougher when they find Sutton has disappeared after their argument and the Mercer family car is missing from the garage. When the police find the car at the bottom of the lake, Emma and Ethan look to each other for support, but Thayer threatens to tear them apart with his accusations against Ethan. Meanwhile, Char's aunt, Rebecca (guest star Charisma Carpenter, "Buffy the Vampire Slayer"), has returned to town and Char is the only one happy about it.
With Sutton’s whereabouts still unknown and a threatening note delivered via Sutton’s signature packaging, Emma is feeling uncertain and on edge. So when she is invited to scout out the University of Texas’s tennis program, Emma surprises her dad and accepts the invite. Nonetheless, Emma can’t escape the fact that her twin may be gone for good. Meanwhile, Rebecca tries to help Char when her mom, Phyllis, has another drinking “episode.”
As Emma, Ethan and Thayer continue to search for the truth of what happened to Sutton at the lake, they follow a lead that raises more questions than it answers. But when a poorly-timed encounter threatens to expose her identity, Emma is left in a precarious position that turns her life upside down. Will she be able to recover? Meanwhile, Laurel impresses the crowd at her mom’s charity benefit with her musical talents, and Rebecca and Alec get to know each other better.
On the night of the country club’s Black and White Ball for junior members, Emma finds herself on the outside looking in, and Ethan must put up a façade in order to protect her. Although their loyalty to each other is strong, the jealousy and lies start to take their toll. Can Emma and Ethan look past their doubts and mend the wedge forming between them? Meanwhile, Laurel and Ted are both left reeling after they discover the motive behind Justin’s actions. And Rebecca and Mads counsel each other on matters of the heart.
Ethan insists on helping Emma get the answers she's looking for about her twin sister. So when a tattoo sparks a memory about Sutton, Ethan pursues an explanation. But the information proves costly when Ethan heads into a situation that quickly gets out of control. Meanwhile, Mads sneaks off to see Ryan, and Laurel continues to see Justin against her parents' wishes.
When Ethan is implicated in a serious crime, he and Sutton leave town and hide out with his father, Ben, on the reservation where he grew up. A burgeoning tension between father and son has Sutton playing mediator, but, despite the awkwardness, she appreciates seeing a side of Ethan that she did not know when they were together. Meanwhile, Emma is left to deal with the aftermath of Ethan’s situation when she must pretend to be witness to a scene where she was not present.
Ethan is still a wanted man in hiding with Sutton, leaving Emma to worry if justice - and love - will prevail. Discouraged by Dan's inability to crack the case, Emma takes it upon herself to find a way to vindicate Ethan. With the help of Mads and Thayer, they search for any lead that may help prove Ethan's innocence. Meanwhile, Ethan and Sutton's time alone in hiding together has lowered Ethan's guard. Sutton uses the opportunity to encourage Ethan to bond with his estranged father, looking to heal her relationship with him at the same time. And Alec questions Rebecca's motives after she agitates Ted and Kristin by offering Laurel the opportunity to produce a music demo.
Caught by the FBI, Ethan is brought back to Phoenix to face charges for murder. As Emma continues to search for evidence that can help Ethan’s case, she clashes with Ted and Kristin over her unwavering support of a murder suspect. Alec’s relationship with the victim prevents him from taking the case himself so he assigns a star prosecutor from his firm, prompting Dan to reach out to an ex-girlfriend who is now a successful defense attorney. Meanwhile, encouraged by their time together in hiding, Sutton has her own plans for Ethan.
Emma wants to find out what really happened on the reservation but Ethan is avoiding her and Sutton is looking to send her packing for good. Curious about his father’s possible link to Derek’s murder, Thayer starts to doubt Alec’s alibi and begins investigating Rebecca’s past. And, Kristin grows increasingly suspicious that Ted is not telling her the entire story when it comes to Justin’s mom.
An unexpected engagement leads to a quickly-planned wedding, causing suspicions that something is awry. Sutton encourages Emma to show Kristin what they found in Rebecca's house. And Ethan makes a discovery that changes the game. Meanwhile, a shocking revelation leads to major repercussions in the Mercer household.
Alec is in jail following his arrest for Derek's murder, but he still manages to unnerve Emma, who is desperate for answers. Rebecca and Sutton's mother-daughter bonding consists of formulating their plans for the Mercer family, which contradicts Emma and Laurel's plan to reunite Ted and Kristin. Meanwhile, Mads goes looking for trouble, and meets a mysterious new guy in town.
Sutton steps up her plans to win back Ethan, and makes a point to let Emma know her intentions. Feeling left out of Emma and Thayer's growing closeness, Mads visits her father in prison and shocks Emma with a family revelation. Dan continues his investigation into Derek's murder, regardless of Alec's arrest, and Jordan starts at his new school and tries to get close to Laurel.
Rebecca advises Sutton to reclaim her life, leading Sutton to challenge Emma to a tennis match - winner gets to live as Sutton Mercer. Ethan is in danger of failing out of school, so Emma offers to tutor him, breaking plans with Thayer in the process. Laurel decides to ask out Jordan, but ends up bringing Mads along on their date. And new evidence comes to light that may exonerate Alec, or may further prove his guilt.
Emma learns more about what happened the night Sutton's car went into the lake, raising her suspicions about whether her sister has been truthful. Ted invites his family to be his guests at an event in his honor and Rebecca orders Sutton to use the opportunity to further their plans for the Mercer family. Meanwhile, Emma heeds Laurel's romantic advice and Rebecca and Alec engage in a game of cat and mouse against each other.
Emma and Thayer further their investigation into the twins' birth mother and what Sutton may know about her. Laurel begins to suspect that something is not right with her sister and makes everyone nervous when she starts asking questions. Using ammunition provided by Rebecca, Sutton lashes out at Kristin during what is supposed to be a peaceful Mercer family dinner.
The Flipside Formal offers Emma the chance to try and trap Rebecca and Sutton in a lie, but she needs Ethan's help to pull it off. Laurel struggles with where her loyalties lie, while Kristin makes a troubling discovery that has more significance than she realizes. Jordan continues to waffle between Laurel and Mads, and Theresa's defense of Alec threatens to drive a wedge between her and Dan. Meanwhile, Rebecca and Ted, and Alec and Kristin, each reminisce about old times.
Emma struggles to make sense of newfound revelations and shifts in her relationships with Ethan and Thayer. After hearing Emma's suspicions about Rebecca, Sutton's faith in her mother begins to falter and she decides to take matters into her own hands. Rebecca is thrilled when Kristin and Ted's marriage continues to unravel, putting her one step closer to achieving her goal. Meanwhile, Alec realizes that Jordan could be a strong ally in his private war with his wife.
Everyone gathers to celebrate Dan and Theresa's wedding but the celebrations do not go off as planned. Ethan figures out who Emma is protecting and confronts her about shutting him out. Sutton's sudden change of heart confuses Emma, who isn't sure she trusts her sister. Ted's behavior grows more erratic as his family continues to fall apart. Meanwhile, in the game between Alec and Rebecca, Jordan decides whose side he's on.
Ethan's confession to Dan threatens to shatter the brothers' relationship forever. Sutton receives a mysterious phone call that may provide some valuable information. Emma's feelings for Thayer are tested when she finds herself in close quarters with Ethan. And someone else comes face to face with Emma and Sutton.
The charity gala takes a somber turn as everyone honors the memory of a loved one. Dan issues Ethan an ultimatum that has heartbreaking consequences. Emma finally confronts Rebecca about her lost childhood. Ted tries to find the right way to tell Kristin about another secret from his past. Meanwhile, an unexpected twist brings the fundraiser to a crashing halt.