There was a brief time when I was in possession of a cat. It was a calico thing; bright-eyed and handsomely whiskered. I was rather fond of it. 

The intonation of the ghost drew my attention from my books. 

"You must get rid of it," he said. 

"Why?" 

"Being occasionally inconvenienced by a man is one thing, but being constantly watched by a cat is another." 

"She can see you?" I realized, leaning back in my chair with frank amazement. 

"Yes," he said. "Now get rid of with her."