Alexander Key’s 1979 standalone young adult novel, The Case of the Vanishing Boy, is the first novel by Key I have knowingly read. It was also his final novel.
How he got onto the commuter train is a mystery to the young boy. So is his name and his past. All he knows is that he is on the run and that it will be very bad for him if his pursuers catch him.
Blind Ginny takes an interest in the amnesiac boy. She cannot see as others do, but she can see as others do not. In short order, she gives him a name — Jan — and something much more valuable: allies.