Mainly in Moonlight
Mainly in Moonlight: Ten Stories of Sorcery and the Supernatural
Colin loved cats and wanted a white cat of his very own, but there wasn't a white kitten anywhere to be found. Thinking that magic might help and knowing that magic occurred mainly in moonlight, he rode one moonlit night to an ancient dead oak which was rumored to be magic. The oak, it turned out, was home to a sorcerer who promised Colin a white kitten if only Colin would serve him for a year ... which he did, sort of.