Innocence by Dean Koontz

Innocence: A Novel - Addison lives beneath the city.  He knows that if anyone sees him, they will try to kill him, not because of anything he has done, but because of what they see when they look at him.  His only contact with others is a priest who allows Addison to restock his supplies at the food bank and thrift store. Gwyneth, orphaned at 13, dresses in Goth and avoids social contact because of her social phobia.  Covered from head to toe to avoid others seeing him, Addison roams the city at night using the subterranean water system.  One night, he meets Gwyneth, recognizing they can help each other while respecting each other's eccentricities, they form a bond that helps them survive.