This only works with Duke 3D v1.3 (ie a non-atomic version of duke3d.grp). The last letter of your bro had worried you. Within the monastery in which he's studying as a novice, it seems strange things are happening. You read again the the end of his last letter: "I fear... There's something...something that hides in the darkness. The others have changed, the Worm has eaten into their faith. Their souls are rotten. I'd like to escape, I oughta save my mental health as long as I can... but I can't, you can't understand, we're not allowed to leave, evil's everywhere... even within myself." You put apart the letter, you wear your boots, you take your gun out from your drawer and while thinking: "My bro's always the same sucker" you decide to investigate on that fucking monastery. When you arrive you enter the monastery, but as soon as you had entered a dark corridoir, the door behind you shuts misteriously.