you need to use a mirror you find in the level. he'll cast his mind control or w/e on 3rd turn (use mirror) and then every other turn after that. its kind of a slog but doable.
the layout change when going out. And yes, it's a pretty "no time lost" escape :/
When the tentacle appear, you have to get up then left, down and going right.
The fork is at the moment when after going right you'll be going south to follow the normal way back to the exit.
This time you'll have to find a way north east.
Look at the map when before the tentacle appear and once it's here when it's time freeze with the text window. You'll see it.