I don't get it - so he believed one could hear the voice of God in the woods, but why drag his son there in the "middle of the night, dead of winter"?
I mean I can understand he was a disturbed man, I just don't understand how bringing Henry [would have] helped him.
I have a guess that might explain why Matthew was so disturbed. Maybe after Matthew and his son had one of their adventure in the multiverse, young Henry stopped aging and became the black death. So Matthew realized their son got exchanged with similar Henry from other multiverse and the wrong one came back with him. He kept bringing the wrong "Henry" back to the woods, even in the "middle of the night, dead of winter", tried to find and exchange their real son back.
Hmm, that would make sense!
You are probably right, I don't know why I didn't think of it myself.
That's too bad, your explanation would have been more interesting than what they actually ended up doing.