The Forgotten Door — Alexander Key

Jon has lost his memory. He can't remember who he is or where he came from.

He only knows he fell through the forgotten door to the strange planet, Earth, and he is in great danger. Injured from his fall, he has to find someone who will help him.

Through his extraordinary power to read people's minds, Jon makes friends with a local family. But then rumors of his existence get back to the army and Jon realizes that the family is in danger, too. Time is running out. He must find the secret passage quickly or he may never get home again.