How does it work? You need the Historical Society key right after meeting Maria for the first time. This lets you skip the hospital and go right to the Historical society. This is done with a trainer, but I’ve heard that the trainer itself may have a virus so I deleted it. However, I have this save file I made so you don’t need the trainer. Just unzip the save files and you will have save games with both Maria and the key. Load the “Town West” save, which is right after meeting Maria in the park, and go right to the Historical Society. This will allow you to play through the whole game with her following you.
Here is the save file:
GameCopyWorld has trainers, but it depends on what version of the game you have, and some don’t seem to work on all operating systems: