The Nothing Month by Cat Miller

Thirty days off-grid. No contact with the outside world. No way to call for help. Zara leaves home to take part in a challenge sweeping the nation no technology for one month.

A body is found in the woods. Right by the Safe House where Zara was meant to check in. And she hasn't checked in.

Another body is discovered, and mum Sally takes things into her own hands to make sure Zara is okay. But when thousands have disappeared, how do you find one missing girl? A pulse-pounding, gripping crime thriller perfect for fans of Catherine Ryan Howard and Jack Jordan.