His entire existence is an utter void of understanding the comings, goings and absences of his only love apart from that moment.
To him, no explanation of time exists gazing out the window for hours on end.
His only hope is a vague awareness that routine of a return exists somewhere in the future.
So on that promise, he remains forever vigilant and alert for that first familiar sound or sign: a key in the door, that affirms his hope and turns it into a wildly wagging tail.