I also agree that you can't put a timetable based on your experience with the other cats. Every cat will have their own timeframe for adjusting. I'm glad you did get the Feliway plug in and that it is working.

This really is a very short time for adjustment. Have you tried rubbing Oliver down with a towel that has the other cat's scent on it? Scent is so important for a cat, you can sometimes calm them down this way and get them use to the other scents.

Another suggestion, is to actually put a scent on the end of Oliver's nose. You can dab a bit of vanilla on the end of Oliver's nose so that he is only smelling that, instead of all the other intimidating cat smells.

It can be a lengthy process to get cats to accept each other. But, you really have to take a time out and slowly introduce them - at their own acceptance rates.

And don't be discouraged if you do have to return him to the shelter. Maybe Oliver would be better in a single cat household., but it's really hard for us to tell at this point in the process.

We're all here sending 'get along cat' vibes your way! Hang in there!