Need to undelete a folder

I have stupidly deleted a folder called "Movies" from my external HD. The trouble is the external HD is connected to my mac mini, and I deleted it from my iMac (browsing the Mac Mini over the network). I thought I was deleting 1 file, and got a message saying the file will be deleted instantly and not moved to trash (since I was doing it over the network), and I clicked Ok.

It turns out it was the whole folder I was deleting, with 500GB+ of movies in it!

Can I get it back?