It's been one year since the brutal murder of her older sister, Zoë, and fifteen-year-old Echo is still reeling from the aftermath. Her parents are numb, her friends are moving on, and the awkward start to her freshman year proves she'll never live up to her sister's memory. Until Zoë's former boyfriend Marc shows up with Zoë diary.

At first Echo's not interested, doubting there's anything in there she doesn't already know. But when curiosity prevails, she starts reading, becoming so immersed in her sister's secret world, their lives begin to blur, forcing Echo to uncover the truth behind Zoë's life so that she can start to rebuild her own.