....for starting a new thread but it may be useful for anyone intending to get the game.
When rescuing LIAN ( and dont worry there are no spoilers here ) you MUST kill the JAILER with Aang and not one of the other characters, AND he must be on his knees when you kill him and not standing up!
I know all that's going to sound like a " wind-up" but if you don't follow those suggestions the game is likely to "crash" and you won't be able to exit the jail!
You'll know if you've done it right because there's a cut-scene right after you beat the Jailer, whereas if it goes wrong you'll get no cut-scene and, as I say, you'll be stuck unfortunately.
Hope that may help someone, and many thanks to "MAC 13ETH" ( on another site ) for finding the solution.