Here's the set-up.
When I take out my contacts, I let the water just dribble into the sink, which makes the cat show up and drink.
Madge loves to be nice to the cat.
The sink in that bathroom doesn't have an overflow drainage hole near the top. The overflow drain is, in effect, the staircase.
Luckily I caught it before the water made it past the door.
The floor and the towels needed washing anyway.