Is there a ghost in our house? what's goin' on?

my fiance' and i lives in the same house, last week the corridor smelled like a dead rat 'though the was house was clean. then the next day the smell disappeared so we thought it was just nothing! then last night we smelled a cigarette smoke coming from the bathroom and when we checked the window it was closed and of course nobody smoked coz we were both watching tv and we're not smokers. then awhile ago i went to pee and i smelled a smoke again, i freaked out a lil bit and told my friance' about it but the moment he reached the bathroom the smell was gone. oh and last week the faucet just opened on its own. what's going on?