When Arabel and the raven Mortimer spend a fun-packed evening with their favourite babysitter, Chris Cross, they have no idea of the chaos they create in their wake. A reckless game of dressing up and hide and seek results in a big crash, a trumpet wedged onto Mortimer's head and a milk shortage.

While Arabel, Mortimer and Chris are out replacing the milk, Arabel's parents return home to find the house empty and apparently ransacked. They fear the worst! Can it be that a black mamba has escaped from the zoo or has Arabel been kidnapped? Policemen, firemen and anxious ladies comb the streets in search of the missing trio, who are blissfully unaware of the chaos they have caused.