There's a trick to this map, you have to figure it out and solve the puzzle accordingly. Redux is a recent revision of an old tech demo that adds more features and improves mapping. Trust no one and no thing.
And as our other dish, you get another release by Dermuda (again consulted with the author himself to ensure that everything is ported correctly and working as it should). Find the Secret Passage and its Redux variant are both single-level Third Encounter scenarios with a gimmick, making heavy use of custom graphics and certain "special effect" features of WolfEdit to create a puzzle in deceptive surroundings. As is the case with such mods, I should not and will not spoil too much; you can deduce enough via screenshots and the mod title itself already! You must remember, though, that the old version should be treated as a tech demo, as it was unfinished and barely tested at the time. Find the Secret Passage Redux is the proper release here, a recent revision bringing more features, better map design and more careful thought to the mod, and it's the one that should be given proper attention.
A minor note, but interesting nonetheless: notice that Dermuda is using a scenario specs template made all the way back in the nineties (I think) by Josh Mills. Over two decades later, I wonder if Josh is around to see that little creation of his still in common use...
===CREDITS===
Dermuda