you know, maybe she ran away to be with him. >> a missing persons case was opened, but nothing came of it. aaron and his brother moved in with ralph full-time. but aaron couldn't move on. she had to have left some trail somewhere. barely a teenager, he taught himself every web search engine, looked for years. but found no sign of his mom online. and a terrible suspicion took hold of him, hardened into something like certainty. his mother must be dead. his father must have done it. >> and after that, it became more of, okay, where would he put her body? >> he was maybe 13 or 14 when he thought about those old coal mines around walsenburg. >> you actually went and looked? >> oh, yeah, i went through a lot of those mines myself. >> alone? >> mm-hmm. >> you're looking for the remains of your own mother. i mean, i can't imagine what that -- >> i can't explain it.