Oh , my God ! What's this ?   What ?   Look ! This window is open .   Did you open it before we left ?   Are you kidding ? It's winter . Why would I open it ?   I don't know . Wait . Is this yours ?   No ! Oh , my God ! Someone has broken into the house .   It looks that way . That's probably why the door wasn't locked when we came in .   I locked it when I left though . 