Ah yes, that bit is a tad tricky. Killing him's the easiest solution. If you really want to be all fair about it, well, here's what you can do.
Leave the camp and start teleporter hopping (I realigned several in the process, don't remember wich ones though, you'll have to experiment.). Make sure to have used the High Hall teleporter at least once.
Go back to the prisoner and you should be able to realign the teleport now.
- Merdarion