By the racket, clambering up into the wardrobe. Bad Cat has learned to open the sliding doors and then through a combination of wriggling and scrambling behind a closed portion of door get to the top shelf where she's evidently constructing an eyrie that Little Monster Cat can't get to. Her mountaineering is going to do wonders for the clothes in there.
An improvement on the 7am wake-up call, where Bad Cat decided to get off the bed, giving me a moment of optimism that I might get an extra hour of unmolested sleep. But no, she decided to empty her stomach onto the bedroom carpet before wandering out into the hallway and deciding that yes, there's a little more still inside.
I'll get up and get the carpet cleaner then, shall I.