My cat is acting REALLY Spooked Out

One of my cats, Monty - who is a 9 month old male house cat, is acting really weird.

We left him last night, as normal - we didn't see him on our bed in the night as he usually is, and this morning he was nowhere to be seen. We heard some meow's and found him in the basement, just sitting there. I carried him upstairs, put him down on the kitchen floor and he seemed TERRIFIED of something, constantly sniffing, taking constant backing up footsteps, always looking to see whats around, then he retreats back down to the basement. So I let him be, went to work, came home and he's still acting the same way.

He's really jumpy too. Normally he'll roll around the floor for hours with a play mouse, but now he tries to swing at it from as fas away as he can and jumps two feet in the air if he moves it!

Something is clearly wrong, although he seems fine physically. This cat is normally as fearless a cat as I have seen and now he is a trembling bag of nerves. What can I do?

His brother, who is normally the scaredy cat of the two is his normal self and is acting fine.

We have no other pets, nothing in the house I can think of that can scare him this way. Please help, I'm worried about the little guy!

Take him to the vet tomorrow. He sounds injured to me. Better rule out health or injury before looking elsewhere for a behavior issue.

I have to agree he seems injured... Also he might of heard a loud sound and scared him... Or he could of eatin something or got bite... Please take him in and let us know...

and if the vet gives you the all clear, try spritzing the house with feliway and honeysuckle. I got new bedding for my new house and the cat hid under the bed, she had NEVER done that. last night I thought maybe it doesn;t smell right cuz it is new so I sprayed it and she jumped right up the bed and went to sleep quite happily.