Smells

I can tell Duncan is peeing in his room. I can smell it, but it's hard to determine where since the whole concrete floor is wet with water smuggled in with ballloons, whose colorful rubbery carcasses litter the puddled floor.

He knows I know too. And it makes him laugh.

If I smell cleaner of any type, it might be my first clue that he's dumped out the brand new jug I've just bought.  Walking towards the bathroom and breathing in a "suspiciously mighty" gust of mint, likely leads to the discovery that he's splashed mouthwash or ssqueezed out the toothpaste. Perhaps taken a bite of your deoderant.

Often too, he smells of onion or something else he can access from the kitchen.

Also, something seems to have died in our attic or air ducts, so that also sucks.