Seventeen-year-old Mia is stranded in the middle of the Caribbean. After a mortifying incident in the school cafeteria, her parents decide there is only one way to deal with her meltdown: move onto a battered sailboat and leave everything behind. Her mom and dad think it's the best decision they've ever made. Mia feels like she's been kidnapped and imprisoned in paradise with no internet and no destination.

Her only hope is to hack together a solar-powered satellite phone so she can call her best friend and fix everything. To do it, she'll have to build a mobile laboratory on the boat and ignore her neurotic mother, who thinks Mia is falling apart.

The problem is, Mia is falling apart. By day, she scours deserted islands, looking for anything she can use to build the phone. At night, she squeezes into a narrow bunk and talks to an imaginary friend. She knows, with absolute certainty, that she needs to abandon her family to save her sanity.

And then two teenagers sail into her world, promising friendship, and maybe even romance. Thoughtful, soulful Alby was raised in Australia but now his family calls the sea their home. The only thing missing is his soulmate. Bold, beautiful Nisha is simply vacationing on her dad's megayacht when a chance encounter upends her life.

Now--with everything hanging in the balance--Mia must decide who she is and what she wants. And with this decision comes the revelation that her past and future are more uncertain than she thought.