Imposter by Bradeigh Godfrey

"Spine-chillingly, jaw-droppingly good!" -- Mary Kubica, New York Times bestselling author of Local Woman Missing Two sisters, a lifetime of secrets
Lilian and Rosie were once the closest of sisters, but the untimely death of their parents pulled them apart. Now, three years on, Rosie has reached out to her big sister, asking to meet. Driving on an icy road in the middle of a snowstorm, Rosie admits that she has something important to tell Lilian—a secret she describes as a matter of life and death. But before she has a chance to tell Lilian, a car careens into theirs, with devastating consequences.
Lilian survives unscathed, but Rosie is left with a traumatic brain injury, unable to communicate. Lilian is convinced that someone deliberately rammed Rosie's car. But why? As Lilian begins to explore her sister's past, she uncovers disturbing secrets that make her question if she ever really knew Rosie.
The closer Lilian comes to the truth, the more danger she and Rosie find themselves in. But Lilian is certain of one thing: she abandoned her little sister once before and will never do so again. Even if it means sacrificing everything.