A door was accidentally left open, and both cats wandered out. Isis is more adventurous, and she may have led Attila a little farther than he would ordinarily go. They weren't outside for long - maybe 20 or 30 minutes, but it was enough time for him to get lost or eaten. (I don't know why I didn't just delete that first paragraph I wrote, except that maybe I wanted to give Attila a posthumous shot-out for being such a brave and adventurous traveler.)
At first I felt only mildly sad that Attila was missing, and thought he may come back. As the days have gone on though, his absence has become more profoundly painful. It's unsettling to watch his (adopted) sister walk around by herself and for one food bowl to remain untouched. I miss seeing him sleeping on the foot of our bed at night, and his easy purr whenever I had a spare moment to hold him or pet him. He is/was one of those pets that comes along once in a while - a truly strange and unusual creature, who liked to play fetch, loved vegetable stems, and enjoyed eating wool, Smartwool socks being his favorite.
I wanted to give him one week before we say our official good-bye to him, but he chances of him making it back now are so slim I'm already mourning him. I do have some happier stories to tell, and good recipes to share, but another day.