Silent Sister by Megan Davidhizar

The must-read suspense novel of the summer about a mysterious sister's disappearance, her biggest betrayal and a deadly truth screaming to come out.  

Two sisters went missing on their class trip—Grace, the outgoing athlete who is friends with just about everyone, and Maddy, the wallflower wilting in her sister’s shadow who'd rather absorb herself in her journal than talk to her classmates.    
 
But when Grace is found—injured, with no memory of what happened—everybody thinks she’s lying. It’s hard not to look guilty with Maddy’s blood on her clothes.  

Desperate to save her sister—and prove her own innocence—Grace must piece together what happened on that school trip with the help of her sister’s notebook and classmates who may not be telling the police everything that about that tragic night.   

She will discover her sister’s secrets can’t stay quiet…but what if her own are the most terrifying of all?