Oddly enough, it was Lucy Lily who unconsciously brought Casey to his rainbow.

Lucy Lily did not mean to do Casey any favor, I can assure you, but Fate just took her and used her for the moment, and Lucy Lily had nothing to say about it.
Don't think that a squaw who wants to live like a white princess will forget to go hunting a gold mine whose richness she had seen,--in a lard bucket, perhaps.

Lucy Lily did not abandon her bait.

She used it again, and a renegade white man snapped at it, worse luck.

So they went hunting through the Tippipahs for the mine of Injun Jim.