Sydney Wells should have died. She was supposed to die.

She never expected, after years of waiting, to receive a heart transplant. Now, seventeen-year-old Sydney doesn’t know what to do with her life. Her daily routine consisted of staying indoors, eating heart-healthy foods, and posting about her transplant list experiences on TheWaitingList with her long-distance BFF (and heart failure buddy) Chloe.

Now, Sydney latches onto the one thing that gives her meaning: learning as much as she can about the person whose heart she inherited. After finding the family of her likely-donor, Mia, Sydney falls deep into her world—and may also be falling for Mia's best friend, Clayton.

But Sydney isn’t the only one hiding something. Mia’s brother Tanner won’t talk to Clayton, and Clayton won’t tell Mia why. And hundreds of miles away, Chloe’s health has taken a turn for the worse. Sydney needs to face what’s in her heart—the truth, the guilt, and the future—before it’s too late.