My cat is puzzling me

My cat is a 14 year old fixed male tabby in fairly good health. Through his life he has come in and out as he pleases. For the past week he has wanted to stay outside, but he will sit by the door and meow to come in. When we open the door, he will stand on the threshhold, but remain outside. If I carry him in, he will immediately want to go back out. Last night we put him in until he pulled down the curtains trying to get back out. He has never done this before and I am starting to get concerned, he appears to be healthy except for this insane behaviour. Has anyone ever seen a cat do this before? I am starting to get concerned. There are no new members to the household,and no changes at all but my wife is 12 weeks pregnant. What the heck?

What about installing a cat door so he can go in and out at will? You can always block it off at nighttime so he has to stay indoors. It could be he has an intruder outside and you haven't noticed the new cat yet, but he has. At least tearing down the curtains is indicative to this type of behaviour.

Thanks, we will look around and see if any neighbors got a new pet or something. We have a dog too and he does not seem to be on edge as if there were a stranger around.

If it is a feral cat, there will be no one around to claim this cat as theirs. It may be why the drapes are being pulled down, the musky scent of a feral can send some cats into a tizzy.