Joining Multiple Files in same directory

I know about batch joining files etc....the problem I have is a bunch of shows that have been downloaded to the same directory from youtube , each episode is made up of 4 parts. So I have say 30 episodes in one folder and I would like to batch join all these files individually into their individual episodes, how can this be done. I see there are many programs that will batch join a whole bunch of files but then you end up with just one big file. I'd like to perform a batch job but keep the episodes seperate from each other. Maybe that's too much to ask... any help would be appreciated.

thanks
Pete