He seems to be fascinated by the three cats who live INside the house. In return, two of the indoor cats are carefully monitoring his behavior. In fact, one of them, Remus, is possitively obsessed. He paws at doors and windows when he knows Nacho is on the other side. He paces the house in search of the best window by which to track this interloper.
Once, Remus got out and gave Nacho a few hearty bats to the head to let him know who was in charge. Oddly both are large, black, and relatively old.
I so badly do NOT want another cat.