the unfamiliar cry...

Last night when I was taking the bath I heard the animal's scream from outside, must be the cat's cry. I opened the window but couldn't see who was crying. Maybe one of our familiar homeless cats.
This evening, mother told me that in daytime she saw an unfamiliar, unneutered big orange cat in our garden. "Our" homeless cats were also there but they were just looking at it cautiously and did nothing, mother had to chase it away. So the scream of last night might be caused by that orange cat...
But... doing nothing to an unfamiliar cat? Now fed by humans everyday and allowed to be relaxed anywhere, our homeless cats seem to become softer! X(