Tigger has been escaping!!

And I have no Idea what to do!

For the past 3 or four nights, apart from x mas eve thank goodness, Tigger has somehow been sneaking outside while we are all asleep. I have no clue how he is getting outside, and its freaking me out!! He has just been turning up at my bedroom window in the early hours of the morning- and nobody has been letting him out, I never ever let him spend the night outside, EVER, but he has obviously found a way. The only possible way is we have a busted window - but its very high up and I cant figure out a way he could get down safely. I'm gonna shut up that area of the house tonight anyway and see what happens. I'm just thankful that the nights he has gotten out, he has come home safe and sound!

Never underestimate a determined cat. Are there any other holes? maybe under a cabinet or into a crawl space that he could sneak out of?Since he can't get back in on his own, the window if probably it.
Another thought to worry about, if he can get out - can anything else get in? ...probably best to fix the window soon.