The Big House book by Carolyn Coman

When their parents are sent “up the river” for embezzlement, Ray and Ivy are left to live in the lap of luxury with Marietta Noland and her ancient husband, Lionel. But life at the big house is not all it's cracked up to be. First there is the shrouded portrait, then there is the spider in the decaying wedding cake. And what about the vicious instrument Marietta uses to decapitate her egg? When "the rain in Spain" begins to fall (in other words, Ray wets his bed), things go from bad to worse and Ivy knows it is time to take matters into her own hands. What follows is a hilarious lark as Ray and Ivy case the joint, get the skinny, and show Marietta she has met her match.