I See Souls as Angels or Demons

Erin has been able to see the color of people's souls since she was a child, with red marking goodness and black marking evil. At six years old she refuses to be taken in by the polished but black-souled Monicas and instead goes home with the plain Helens, whose souls shine red. Their disabled son Daniel cannot walk, so Erin devotes herself to caring for him as his faithful little helper. Years later, a girl the Monicas consider their real daughter arrives, resents Erin, and begins scheming against her.