What happened to Christine Collins' son?

It was actually never known what happened to Walter Collins. Upon seeing the movie, it certainly looks like he was murdered at the ranch along with as many as nineteen other young boys. In real life, though, Gordon's mother supposedly had something to do with the murders as well. Rumor has it, that when Walter was caught trying to escape, she, herself, murdered him. No one ever found out if Walter was murdered, or escaped and was just never heard from again. But the finger points, it looks like he was murdered, unfortunately.