Welcome to Half-Life: Final Run. Final Run takes place after the "Apprehension" episode in the original Half-Life. Instead of being thrown into that trash compactor, you are transported to the Black Mesa Jail. Here follows the new radio transmission: "So where are we going with this Freeman guy anyway?" "Topside for questioning." "What the hell for, we got him. Why not just kill him now?" "Because command already knows we're bringing him in. I don't need to be answereing how we "lost" him again." You awake from your beating bruised and dazed - the staccato of an assault rifle slowly winding down. Taking in your surroundings it appears you're in a small brig built on the base. A firefight had broken out between several security guards and the small squad of Marines in charge of the brig. During the firefight the locking mechanism for the cell doors is damaged. You can now make a Final Run for freedom.
Second image is odd in the fact that it exists. I compiled the jail map, walked through the level change and wound up here. Keep in mind I never compiled this map - it just kinda plopped me in it. I couldn't move though even if I NOCLIPPED. But here goes to show you my horrid mapping skills back in 2004. I could make prefabs no problem - maps? ewww. Just ewww. And this is "level 2". You'd be attacked by a few HECU and a headcrab, round the corner - HECU, drop into a sewer, walk a few feet and........you guessed it - LEVEL CHANGE!
Haha, that's unusual. You must have compiled the map at some point however, otherwise there would be no way it would run in game. :P
It must be some kind of "hidden" code in the first map itself. Maybe like a pre-cache of sorts. This map was compiled, but it was YEARS ago. I only moved the first map to Jackhammer and compiled it recently.