When eleven-year-old Eddie Dickens's ill parents become "a bit crinkly round the edges," he is taken by his great-uncle and great-aunt, Mad Uncle Jack and Mad Aunt Maude, and embarks on adventures that involve strolling actors, St. Horrid's Home for Grateful Orphans, and a carnival float shaped like a giant cow.

Leaving his parents, his Mad Uncle Jack, and his Even Madder Aunt Maud at home at Awful End, Eddie Dickens, along with the color-blind Lady Constance, boards the ship the Pompous Pig on a mission to America.