I'm not starting with Underworld halfway done. I start exactly where the game starts. It's just that there's two triggers at the end of Prologue: one that takes you to Mediterranean Sea, one that takes you to Mexico, which is halfway through the game.
Here's a video that explains it, in case anyone cares enough to understand how the start of the Underworld run works: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-8UWL3KTmdB8.html