Screeching cat for no reason

A friend is fostering a wonderful, sweet, and loving cat that she wants to adopt (neutered male just over a year old). She already has two cats, both males and both neutered (one is 8 years and the other around 3 or 4 years old). All three cats are from shelters and the oldest is declawed (declawed by previous owner).

The two previous cats get along wonderfully and have since they were first introduced to each other around a year or two ago. The foster cat gets along wonderfully with the middle cat, but the oldest cat just will not accept him. (My friend used the introduction process we suggest here and followed it to a T.)

Anyway, I thought my friend was exaggerating about the problem until I heard with my own ears this afternoon what happened. Old cat was sitting on the floor when foster cat walked by. Foster cat did nothing more than glance at old cat as he walked by. In response, old cat did the most blood-curdling scream you could imagine. No hissing, no swatting, but an awful screeching scream.

I'm stumped! My friend is hesitating to adopt this wonderful cat because old cat is so upset. Is there anything she can try at this point to make things better? (I hate the thought of taking her foster to PetsMart at this point because he has been with her for about 2 months now.)

Can't say I have heard of a reaction quite like that - has she had the older cat to a vet? I am wondering if it is neurological prob but where he is still quite young, that seems not likely but you never know. What about Feliway? Has she tried anything like that?

That sounds familiar - Jamie reacts to other cats with a blood-curdling scream, and then launches into a physical attack. Sorry, I really don't have any advice, other than to start all over with the introductions. It hasn't worked for me, but that doesn't mean it won't in your friend's case.

Thanks guys! I'm going to her house this afternoon. I will suggest feliway and I don't think she has tried the vanilla trick yet. The older cat is healthy and reacts this way only with the newcomer. I neglected to mention that because the newcomer is still so very young and kittenish, he tackeled the old cat a couple of times early on --- not aggressively, just in play, and learned not to do that any more. He now plays only with the middle cat.

Hopefully Mary Anne will see this thread and have some sage advice!