Pathologic takes place in a single town, over a period of 12 days. That's defined from the start. You won't understand why, but there's a reason. There are three playable characters, all healers of some sort, each experiencing a different side of the story. The ones you don't pick appear as NPCs, merging seamlessly with the rest of the cast. You'll interact with these characters on a regular basis, but although they'll guide you to an extent, for the most part you're totally, ruthlessly alone.