Dark Peak — Marcus Sedgwick

Super-Readable Rollercoasters: Super authors, super accessible, simply super-readable fiction One long, hot summer, two children disappear on a school trip. One child is eventually found, but Porter is worried that no one is even looking for the other, Stephen, anymore. Why can no one remember who Stephen is? What happened on the school trip? And why does Porter get the feeling that supernatural forces from deep in the past are at play?