Hissing after outside

Question
I have two 6-year-old indoor cats that have never gone outside.  Yesterday my male escaped for 12 hours.  Ever since I have gotten him back outside my female has been hissing at him.  She won't even let him get near her.  Does this mean he encountered other animals outside?  Also, how can I get the female to stop hissing at him?

Answer
Hi Mandy.  Your male probably brought in strange scents from the outdoors.  He may have encountered other animals outside, but even if he didn't come in contact with any animals directly, he probably picked up the scents of other animals from bushes, etc., that your female can now smell on him.  I would separate the two for now until she has a chance to calm down.  It could take her a couple of days, so this may mean purchasing an extra litter box if you don't have two.  You may also want to bathe your male to try to get rid of some of the scents that may be upsetting your female.  If the male gets too upset with bathing, you can lightly dust him with talc-free cornstarch baby powder.  This will help mask some of the unfamiliar scents he may have picked up.  It's also non-toxic and will make his coat nice and silky.