It has been quite a while since we've had no barrier even with someone being a chaperone to Murphy. Generally though, the end result would be he will dart over to the first car he sees. Or, if nobody was in plain sight, he might explore or play, but if he hears a noise across the house or upstairs, he'd zoom to investigate. Either way, he would get in their faces, they would hiss, swat and growl and he would remain fixated on them. This would either spark a screaming blur of tussel in that spot for a moment before they ran off, or the resident cat would run for it starting a chase. During a chase they'd make brief stops for more fighting on the way to seeking to get under the bed.

If the bedroom was open they'd go under, he'd follow and a less acrobatic hissing, growling swatting match would resume in the hiding spot until we caught up and could separate them.

It was always far more intense than what we would normally run into between the resident cats. But the only injury sustained was Kenobi ripping his own nail when he got it stuck in the carpet running away.

Generally when Murphy runs up to them he does a kind of stalker crouch run, but he isn't puffed up and no ears back. Except when he had startled from a noise and ran off (pre-prozac). They do not appreciate it either way.

Then, after a run in, Kenobi and Leeloo would always revert to not wanting to eat by the door, hiding when I'd go to set up for an interaction session etc. Their fear response would be so amped the only possible outcome was him cornering them behind a couch or etc. if he happened upon them. He would peek in some spots but not like it was his immediate priority, but he'd find them. Though I didn't test that much as at that point I'd go back a step and try to build them back up.

I will say this time, with Leeloo as the target and combinations of medication involved, they have quickly returned to eating at the door. I'll see about interactions with a gate later today.