For now, he seems stuck in a holding pattern, spending most of his time curled up in one of those wonderful cat-circles, with his head resting on a paw, safely tucked away under the bed in our guest bedroom. My morning routine now consists of (1) make coffee, (2) empty the litter box,
(3) give Sam and Harley some 'greenies' (cat treats that clean their teeth) and (4) lie down on the floor next to the bed where Caruso is hiding and spend some time petting him/talking to him. At first, there was no reaction from him, but now he starts to purr almost immediately, which I'm hoping is a Good Sign.
Whenever he's moving from one spot in the house to another, he announces his intent with very loud yowling, as if to warn everyone away. I've managed to pet him when he's hunkered down under the dining room table, and even to catch him and hold him a couple of times, but for now, he's very much the phantom cat living in our home.
C'mon Caruso! We like you a LOT, and would love it if you'd join the tribe!