I totally hear you on the first-floor home-alone nerves. Also a single person, single story house, lived in a first floor apartment with an enormous glass patio door before that -- there's a reason I keep the fist-sized dowel rod aka junior baseball bat for spring window-opening right beside my bed instead of in the windowsill like the others. It's for thumping whoever breaks in. ...and who isn't the cat banging around chasing a moth at 3:30 AM grargh.