Frances and her older brothers long for the approval of their distant scientist father. When 12-year-old David steals a bit of experimental waste material during a laboratory visit, Frances makes him share it with her. Although she is too young to understand how to conduct a proper experiment, a fortuitous combination of factors causes her material to grow into a sentient creature. Afraid that either she or the strange animal "Monnie" will be punished, Frances enlists some school friends and the gardener to help her hide the creature. But for how long can they keep it concealed? Especially since Frances' nervous behavior is sufficient to be noticed by even her usually-indifferent parent.
In addition to the more exciting monster plot, Alcock does an excellent job developing nuanced characters and having them interact and misunderstand one another.