L. Frank Baum and the Perfect Murder

The story starts with a cold blooded murder and two children finding a small bag of jewels, money and three severed fingers. Fourteen years later, L. Frank Baum, one of those children, has an orphaned friend, Willy. Trying to trace Willy's parents, they come across the unsolved murder of the millionaire Matthewsons. Clues lead to a cousin, Professor Mombiton, who will inherit millions if the Matthewson child does not turn up by his 18th birthday, only a few months away. When Frank and Willy interview Mombiton his fear of being found out is aroused. So who else does he kill? Can they prove his guilt? Do either of the young men escape his machinations? Is Willy actually the Matthewson heir?