Dora, Oswald, Dicky, Alice, Noel and Horace Octavius (“H.O.”) Bastable are desperate to help their widowed father to restore the family’s fortunes after his business fails. Their moneymaking schemes, from digging for treasure in their South-London garden to becoming highwaymen on Blackheath, mainly lead to a good deal of trouble, until one adventure promises to change everything…