The Witch is sick so Simon and Jimmy call her sister who promptly arrives from Africa with her familiar, a gorilla called Banana, to bring medicine. The gorilla quickly escapes and causes mayhem, disrupting Cuthbert's game of chess with his aunt and scaring Simon's mum - the boys in close pursuit. George the cat finally returns home after eating priceless museum furniture, leaving a trail of sawdust for the police to follow.
