Three Australian nine-year olds from different immigrant backgrounds form a Secret Society they call The Threefold Cord, to do good such as helping an old lady. When they rescue a tortured cat, they stumble on a crime gang that traffics costly cats and smuggles rare red diamonds, led by the enigmatic and quite monstrously fearsome Dr Vandersluys, the tall, pale stranger who always wears sunglasses and dresses in black.

Through their unity, courage and resourcefulness (and helped by an Aboriginal elder), the three succeed in saving themselves, overcoming evil and helping others.

The story is thrilling and funny and full of unexpected twists and turns and mysterious characters.