Black Queen (P)

The 'Black Queen' is what Billy calls his shadowy next-door neighbour. She always wears a black cloak and a wide-brimmed black hat. She lurks about her garden, alone except for her black cat. Scarily for Billy, the Black Queen befriends him and asks him to look after her cat while she's away. Billy can't resist the opportunity to peek inside her house. There are chessboards scattered everywhere. Who is the Black Queen and what sort of game is she playing? Billy thinks he knows...