We did take it to the vetrinarian for an inspection, before we build the pictured gaol for quarantine. The animal was pronounced free of all parasitic infestations except fleas, with which it was fairly riddled. After a round of partially successful shampooing misery, most of the fleas migrated to the face, where they became irretrievable, and we had to go back to the animal hospital for another dosage of anti-flea poison on the back of the neck. We're told to wait a day and she can be safely released into the house. I understand that the flea treatment works by making the fleas infertile; I suppose I can bear seeing the odd critter on the floor in some of the less furnished rooms of the house, for a while, but not let the animal roam freely in the closets and bedrooms just yet.
We've decided to call her Mikan after the label on the cardboard box we used to bring her home. She spends most of her time caterwauling like a door hinge, pausing from time to time to vomit. I suspect she had gone without real food for some time, but we have the special cat milk to mix in with moistened chow, and she just inhales it as soon as it's put down. She should be relatively healthy and parasite-free in due course.