Charlie is part of the community of mole people in the tunnels connected to Brooklyn Bridge Station. Charlie takes care of infrastructure for the mole people and is referred to as the "Lieutenant Mayor." Recently, the mole people lost their supply of water due to an explosion on South Street, and the path to the valves in Brooklyn Bridge Station that can be used to restore the water supply has been blocked by a cave-in.
Charlie Fann is a regular guy, down on his luck. He lives in the Brooklyn Bridge subway station, which has been closed for quite a while. He's good at avoiding the notice of the police, the NSF, and anyone else who might make his life more interesting. Show him a problem and he'll fix it. If he can't tackle it himself, he'll negotiate for the solution if possible. This has made him a big man among the mole people of New York City.
You'll find Charlie to be a reasonable person, if a little bitter about his current state of affairs. That's fair — he doesn't ask for much. A dry place to sleep, neighbors who don't have Gray Death... and a working bathroom. It's that last one that unfortunately hinges on a working infrastructure that no longer exists. He keeps informed about affairs that might have something to do with his people, so he's up on most things that happen in or off the deserted subway lines.
In the Brooklyn Bridge Station, talking to Charlie initiates the secondary goal of restoring the water supply for the homeless living in the tunnels.
After completing the mission, Charlie will provide the code (5482) that unlocks a secret passage in the women's restroom which leads to the tunnels. He will also provide information on recent NSF activity.