Imp encounter?

Hello everyone! I'm new to this website and had a quick question! I've had Doom 2 for 6 years, and haven't beaten the game yet (I know, lol) due to school, college, ect. Well I didn't have anything to do, so I started a new game and beat missions all the way to mission 25 "Bloodfalls," I believe. Well, I beat it, then it restarts me on the same exact level, except the mission is called, "Imp encounter." Is this a glitch or something? Because I read they have 32 levels. Anyway, thanks to all who answers, and please bare with me, I'm new to actually playing the game and this website, thanks! :D

impse joek?

I didn't use any wads, just the single player game, nothing more.

That definitely ain't right. How did you obtain this copy of Doom 2?

A friend burnt it on to a DVD for me 6 years back

Quite possible it's an altered copy of it. Map26 should be Abandoned Mines.

Thank you all very much. The cheat "idclev 26 allows me to skip to the next level, " abandon mines."