“Opossum's Favorite Restaurant”

Rick McPherson at Waterford Country School (to whom I was referred by Groton's animal control officer) says to just let him go.

So basically, the little rat got a free meal (cat food), and warm place to sleep for a little while (my office), and now can just go on about his business. I'm sure he'll be back... in a few days there will be a whole herd of them at my door.