Background Story to this mod: In the tutorial level of Mirror's Edge, Merc talks about your fall that took you out of commission for a while. The map (available at ModDB) is a prequel to the game and explains why Faith got injured. The level starts off after a long day of work, but it's not over yet because Faith gets a call to do some overtime. You must retrieve a bag inside a building that Celeste hid there because she dropped out, so you need to finish her assignment instead.

Cool indeed.