Is this a valid log line? Or is it too vague and too long?

1: Who is the lead character?
2: What event sets the lead character in motion?
3: What is the goal of the lead character?
4: What is standing in his or her way?

There are some elements missing from your logline. Your lead character seems to be “Investigators”, Not, a nosey paranormal investigator, not an atheist news reporter… Investigator? For an insurance company? For a gossip magazine? A police investigator? An FBI agent? A hard-boiled detective? Give us something the reader can picture in their head.

Also, what does ‘a place feared’ mean? A graveyard? A spiders den? An eerie cave? A Miley Cyrus concert? I have no idea what ‘a place feared’ looks like on screen. Again give the reader a mental picture.

You also haven’t told us what specific event set’s the lead character into motion? Instead, you talk about ‘past malicious activity’, but how does that relate to being possessed by a stillborn baby?

Finally, you give us no hints on how a stillborn baby can possess anyone? You might want to give us a word or two, to at least hint at how a stillborn baby could possess anyone.

In the end, the logline should answer the 4 questions up above and leave the reader wanting more, It should not lead to confusion and more questions.

Good luck with your story, it sounds interesting. Everything I have mentioned relates to the logline, and has nothing to do with whether the story itself is good or bad.