Good news for Fred!
Three days and $600 later, I just retrieved Ivan from the vet. He made a beeline for his scratching pad in search of catnip.
I feel pretty guilty, and have to be more careful. He'd escaped about three days before I went to Indiana, and my neighbor brought him home, saying he'd been fighting in her carport. I didn't even know he'd gotten out. It took me a couple days after getting back to notice the abscess, and by then it had gotten bad. This is the second time in three months he's made guest appearances at the vet for the same thing, but last time I caught it the day I left for Chicago and just dropped him off at the vet on my way to the airport.
I'm supposed to give him ten-minute warm, wet compresses a few times a day. Have you ever tried to hold a wet washcloth to a cat? We'll see how this goes. Right now he's purring wildly at my side, so all's good for now.