Nine teenage girls are en route to Hawaii when their plane fails, leaving them stranded on a remote island. Among them we meet Leah, who has survived to tell their story to a pair of federal investigators. Flashbacks offer an intimate look at Leah’s pre-island life, and the taboo relationship that broke her heart.

The castaways are still reeling after a tragic event. Frustrated by everyone else's inaction, Rachel leads an expedition to the island's summit to get a lay of the land. We learn more about her career as an elite athlete, the extreme measures she's taken to succeed, and the brutal truth that she isn't sharing with the others.

Leah, Rachel, and Nora swim out to the plane wreckage and return with a crucial find. Fellow Texans Dot and Shelby search for a cave that might provide better shelter, but their contentious relationship makes matters difficult. Flashbacks reveal heart-wrenching secrets about Dot's home life.

A shelter-building contest turns ugly. Toni provokes strife on her team, and we'll learn in flashback that this isn't the first time her rage issues have caused devastating harm.

When one of the castaways goes missing, a search party heads out to find her. We learn more about Fatin's past, which isn’t exactly the glamorous thrill ride the others thought it was. At the end of their exhausting day, the girls make a shocking discovery that stokes Leah's doubts about the island.

A sudden illness rips through the beach camp, affecting nearly every castaway. As the girls fight for survival, we learn more about Leah's past and how she’s been faring since her rescue.

A tidal surge forces the castaways to relocate their camp. Still suspicious of the island and how they got there, Leah turns her paranoia on one of the other girls, viciously accusing her of knowing more than she's letting on. In flashback, Jeanette's astonishing backstory is unveiled.

Assuming that rescue is imminent, the castaways let loose. The only girl who doesn't feel festive is Shelby, and a look into her past reveals why.

Starvation becomes a very real possibility for the weakened girls. Martha could spare them from that fate, but it would require a sacrifice she's not prepared to make. Flashbacks take us into her past, revealing the childhood trauma that's made it hard for Martha to grow up and rise to difficult challenges. Leah's paranoia about the island escalates to a fever pitch.

On the island, Leah feels closer than ever to proving that someone's behind their predicament. Post-rescue, fed up with the tight-lipped authorities, Leah goes searching for her own answers.

The stranded girls grieve one of their own. Meanwhile, we learn they’re not the only ones ensnared in this social experiment—it turns out there’s a male control group, marooned on a different island.

The girls struggle to adjust to their new camp, while food scarcity plagues the boys. Raf gains confidence thanks to a new friendship, but flashbacks reveal the dark side of his codependent nature. Post-rescue, Leah makes an unexpected ally.

A brush with death rattles the girls. The boys must defend themselves against a blood-thirsty predator. In a series of flashbacks about Scotty and Bo, we learn how the world has tried to grind them down, and why it’s hard for them to trust the other castaways.

The boys continue to battle against the dangerous predator, and this time they plan a coordinated attack. A birthday on the girls’ island puts everyone but Rachel in celebratory spirits.

Rachel seeks necessary closure, while Fatin makes an unsettling discovery in Nora’s journal. Meanwhile, an incident comes to light that sends shockwaves through the boys’ camp, altering their life on the island forever.

Now that they’ve expelled an alleged criminal from their ranks, the boys clash over how much mercy to show him.Ivan’s past choices back home have impacted his life and those around him. Over on the girls’ island, Leah’s mind starts playing tricks on her, while Martha’s past comes back to haunt her in a catastrophic way.

The girls relocate to the hot springs, but the perilous journey shatters the group and Leah is driven further into madness. The boys manage to come to a truce, but it’s upended when troubling secrets about their most controversial member come to light.

Each girl on the island is engaged in some kind of struggle to find peace and the truth. Meanwhile, the boys must decide whether or not to attempt a dangerous trip.