'What's that smell?' says my 16-year-old.
My eldest has just returned from his second term at university. He is standing in the kitchen unzipping an enormous bag of dirty washing.
'Oh,' he says, looking slightly uncomfortable. 'I think it might be my clothes.'
There are many aspects of student life my eldest has wholeheartedly embraced - cheap pints, late nights, the boxing club. But washing his own clothes hasn't made the cut.
He and a friend recently tried to save money by cramming their laundry together into one tiny machine. They ended up with the same grubby T-shirts, but slightly damp and sprinkled with washing powder.
'OK,' I said wearily, 'let's get it in the machine.'
'I think I'd better do it,' he said. The ripe smell was overpowering.
After we'd bickered about separating light and dark colours, which he thinks completely unnecessary (depending, I think, on whether you like your white shirts a kind of dismal grey), he put on the first load and I looked anxiously out of the window. The sun, I've noticed, always disappears when your student son is about to hang out a term's worth of socks.
'I can still smell it,' says my 16-year-old, wrinkling her nose with distaste.
It was only at this point that we noticed a small heap of earth on the floor. The kitten still gets confused about the difference between earth indoors and earth outside. It seems to her completely logical to crap in the plant pots.
'So it wasn't me!' says my eldest delightedly.
'But it's interesting, isn't it,' says my daughter, 'that you thought it probably was.'
I want to say, remembering all the dirty washing strewn across her bedroom floor, that it's a case of the pot calling the kettle black.
But I don't say a word.
Catch up with previous Surviving Teenagers columns here.