He fumbles with the deadbolt, but sees that it’s no use.  It’s a double-lock, the kind where a key is needed both inside and out.

He scrambles back through the living room, sees a hallway and ducks into a dark room.  It’s a bathroom, for he nearly slips on the hard tile and rams his foot into the side of the tub.

He slams the door shut, flips on the light, and searches for a lock.  This one has a lock on the knob.  He pushes it, knowing it won’t save him much in the event a psychopathic madman wants to bust his way inside.