Can anyone help me narrow down this case?

That description alone may not be enough to identify one case reliably, especially if some details have blurred together. Do you remember roughly when you saw the episode, the show or channel, where the case happened, or about how old the child was? Any one of those could help narrow the search.

I’d search episode guides and case summaries using a few separate details rather than the most disturbing parts of the memory. Try combinations like child, neighbors, couple, and coming home from school, then check whether the episode actually matches before settling on a name. It’s easy for details from different stories to get mixed up.