Growling Cat

We have two cats, one is male and one is female. Both are housecats who have never been outside in their lives (other than transport in a carrier). Recently the male cat fell off the balcony of our apartment, and before we noticed that he had fallen, he was long gone. We put out fliers and talked to all our neighbors, etc, and luckily he ended up being found by the maintenance crew a few days after he went missing. He is now returned, safe and healthy.

The problem we're having is that now the female cat is extremely unhappy about him being back. Any time he goes within 10 feet of her, she either hisses with her mouth wide open and teeth exposed, or the sits there growling repeatedly like a motorcycle revving its engine. The male cat has always been the submissive one, so he just stands there and doesn't do anything about her threats, although once they did come roaring thru our bedroom while we were going to sleep. It sounded like a couple of lions fighting as they ran across our bed, and they did scratch up my arm.

Anyways, does anyone have any ideas on what we can do to get the female cat to accept him back without growling all the time?

He was only missing three days? You are extremely lucky he was found safe and sound.
It sounds like what is happening is that your female does not recognize him. Cats go a lot by smell. After being missing for a few days he will not smell the same as he did before. Those smells are unfamiliar to her and are upsetting her.
What you could do to try to alleviate the problem is to either: put baby powder on your hands, rub them together and then run your hands over both of your cats. This makes both of them smell the same; or you could try a little dab of vanilla under both cats chins and near the base of their tails; or you could rub a towel over your female to pick up her smell and then rub it over the male. This should help settle her down.
If this doesn't work you may have to do an introduction as if they are brand new to each other. This is my favourite site for giving info on how to do the intros properly.....

http://www.squidoo.com/multi-cat-management

Can you tell us how long you've had the cats. Were they kittens when you got them or adults? Did you get the cats at the same time, or did you have the female first? What was their relationship with each other like before the balcony incident? Did they genuinely like each other, cuddle together and groom each other?

Suggestions 14K gave are good ones. You might also try playing with them both with a teaser toy.
http://www.nextag.com/cat-teaser-toys/compare-html

Sit on the floor and flick the teaser from one to the other. Give them equal time to play, going from one to the other and then give them some treats. Or put a toy on the end of a string and drag it around the house. The interactive play gets their minds to focus on the toy and helps to stop the obnoxious (growling) behaviour. Be persistent and keep the sessions fairly short, 15 mins. at the most. Hopefully when you have your girl interested in the teaser toy, if she starts growling at your boy, you can redirect her with the teaser toy. Good luck! :fingerscr Let us know if this works.

Both are about 4 years old. We got them both as kittens, one week apart (the female first). The female cat was always the dominant one, and was generally anti-social, but the male cat was always very submissive so they basically got along fine.

For the most part they just co-existed peacefully without REALLY liking each other. But they did occasionally groom each other, and often chased each other around playfully, etc

I think 14+ is right on, your male probably smells a little different after being outside for three days and your female thinks he is a brand new cat.

I use catlover's suggestion of distraction with toys when Sweet Pea is stalking Puddles and it does work very well.

Ok, so they're friends, but not bosom buddies. Your girl should resume her normal behaviour to him---give her another week. But if her growling looks like it's going to continue to be a habit when she growls immediately say "Psssst" to her and then "No!" (don't use her name) and give her a hard stare. Sometimes that's enough to stop it. It shows her you don't approve of her growling. Most cats like to please their owners and hopefully she'll get the hint her growling to your boy bothers you.