Mulder and Scully investigate the death of a severely disabled girl, and find a mystery involving angels and demons.
Continuity Nod: Scully's biological daughter from "Christmas Carol"/"Emily" is mentioned.
Evil Redhead: Aaron Starkey, the kind-hearted Social Services agent, is Satan incarnate.
Extra Digits: The episode starts with a girl who's shown to have six toes on her feet. The case becomes about the mysterious deaths of several girls (including this one) born with six digits on all four limbs (some had the extra fingers removed to better fit in).
Light Is Not Good: Subverted. The angel may be killing the girls but he is taking their souls to heaven as they are nephilim.