@(you need an account to see links) AHHHH NEOQUEST II my favorite game of all time
Once you leave the dark cave, you need to take the bridge to the far right of the screen.
If you're not using In-Depth Neoquest Guide, you should be - it's a lifesaver!!
This page shows the bridge you should follow:
(you need an account to see links)
---------- Post added at 06:05 PM ---------- Previous post was at 06:01 PM ----------
Oh, and if the portal is gone, @(you need an account to see links), you'll need to walk back out the cave through the entrance you came in again.