It’s a well-known fact that cats see and hear things that aren’t there. I’ve often observed Olive running through the living room at night, swinging at some invisible opponent and trying to climb the walls to reach some unseen object.
She also has a fascination with the washing machine whenever it’s running. Perhaps the clothes inside are calling out to her to free them from their damp, spinning jail cell.
Hazel is of course baffled by all of this. As am I.