Willa lives on the upper West Side of Manhattan with her divorced father and her younger brother and attends fifth grade with her best friend Ruby, and she likes things to be a certain way, because it makes life manageable even with her Sensory ProcessingDisorder; she certainly does not like surprises, and her father has just thrown her a big one: he has been dating Ruby's mother, and suddenly Willa's life seems to be spiraling out of her control--and part of the trouble is that she cannot even explain why she thinks this is a horrible idea, when everyone else thinks that it is wonderful.