Little Billy has been fostered by a rich philanthropist and is off living the high life while Jem and Ned are left in the slums. That doesn't bother Jem though - he's busy pursuing a glamorous life of crime. Having already lost Billy, Ma is bent on preventing Jem following in the footsteps of bungling burgler Uncle Rudd, who is always in trouble with the law and is about to be shipped off to Australia. But when Billy becomes the chief suspect in a robbery at his new home - a priceless piece of jewellery, the Star of India, has been stolen - brothers Jem and Ned jump to his rescue.

In the shady world of thieves and swindlers it takes one to know one, and street savvy, Jem and Ned, apply their skills to turn detective and uncover the true identity of the real criminals: a crooked butler, who is a master of disguise, and his light-fingered wife.