Later she did make it indoors briefly. She had gone to the back porch and napped there most of the afternoon, until some sort of confrontation took place. I didn't see the event but it led to the upsetting of the water bowl and the displacement of the doormat. I don't know which other cat was involved, but I don't think it was Alger. He has been scarce all day, probably hiding out somewhere as he usually does during rain. Had he run the stray off he'd probably have been back almost immediately, and I still haven't seen him.
But the stray, I soon discovered, had returned to the garage after her nap on the porch had been disturbed. I decided to take her some food, and when I went back indoors she scooted between my feet before I could stop her. Luckily she was hungry enough to follow the food back out to the garage and remain eating it when I went back into the house. I don't know what will happen later this evening when Portia wants to go out to the garage for her customary evening outing. I hate to run the stray off, but I can't keep yet another cat around— especially one that wants indoors.
I'm reluctant to leave the garage door partly open for the stray, as any of the big tom cats who frequent the neighborhood could then get in there too. I'll probably run the stray out of the garage tonight and let her take her chances on the back porch. What is to be done in the longer run I don't know. Our local animal control service has limited hours, and I don't think anybody will be available until Tuesday. For now, it looks like Portia and the feral kitties are stuck with a hated step-sister.