As is well-known, Flinteye the Caverman, hirsute haruspex and brilliant spelunker of proto-planetary depths, lost his awesome right arm some adventures back. Thereafter he was gifted with its frisky ghost, practically useless but a pleasure to draw.
Recently he has discovered a green arm fallen from the heavens. With a little watering and oil, it attached comfortably to the site of Flinteye's missing limb.
Additionally, Flinteye dreams of a woman with a backwards arm. She speaks to him in these dreams, but the language is not one he knows. Or rather: she speaks to him in his own language, but he dreams that he does not know this language.
Thus begins "The Adventure of the Three Arms."