Ben, eleven years old and the youngest of the Mallory children, has left his aunt and siblings to come to London where his widower father wishes to introduce him to his young future step-mother. Unable to return home when his brother and sister become ill, Ben is left on his own to explore the maze of walled gardens which surround his new home. Soon he meets Thomas, the son of an exiled East African Prime Minister, and Lil, a fatherless cockney waif. All three children, troubled and contending with the dislocation of their new lives, become entwined in each others’ journeys of self-discovery and adventure.