In the novel five unrelated children talk about their difficulties with their parents' being separated and with their stepfamilies.

The title makes reference to the fictional tradition of the wicked stepmother.

Five children on a school trip stay overnight in Old Harwick Hall, a reputedly haunted house.

However, after a dinner party with her father's friends who also ignore Stella, Claudia attempts to get attention by wearing beautiful green pyjamas bought by Stella in front of the guests, shocking them into politeness.

Before going to bed, the other children secretly place a broken wooden cow made by Richard Harwick into Colin's bag, as a reminder to him to make the best of what he faces.