Where Were They?

In the middle of the night, the human woke up.. catless! There were no cats - or kittens - on the bed. Getting up, there were no cats in the living room, where there are usually at least three. Circling back, there were no cats in the bathtub... Back again, there was no one in the window, no one in the computer room, no one eating or drinking in the kitchen, no one on the dining room table, no one under the dining room table... It was seriously mysterious! The human considered the checking out the basement, but she was sleepy, barefoot and virtually blind, so instead she went back to bed. But where were they? And whether it was the basement or - more probably - another dimension, what were they all doing?? (She asked them in the morning, but nobody was saying.)