There are several reasons for this little book, but the best of all is the main reason—that it is a cracking good story, and right out of life. The characters will be found interesting, and they are real people, every one of them. The incidents are full of action and color. The plot has mystery, surprise, interplay of mind and motive—had a novelist invented it, the reader might declare it improbable. This is the kind of story that is fundamental—the kind Mr. Chesterton says is so necessary to plain people that, when writers do not happen to write it, plain people invent it for themselves in the form of folk-lore.

But apart from the story interest there are other reasons.

When the New York police department had run down all the threads of the plot, and accounted for most of the characters by locking them up, they had become so absorbed in the story themselves, as a story, that they thought the public would enjoy following it from the inside.

While the crime was being dealt with, the police were subjected to pretty severe criticism. They felt that the facts would make it clear that they knew their trade and had been working at it diligently.

The story gives an insight into real police methods. These are very different from the methods of the fiction detective, and also from the average citizen’s idea of police work. They ought to be better known. When the public understands that there is nothing secret, tyrannical or dangerous in good police practice, and that our laws safeguard even the guilty against abuses, there will be helpful public opinion behind officers of the law, and we shall have a higher degree of order and security.

The directing mind in this case was that of Commissioner George Dougherty, executive head of the detectives of the New York Police Department. Thousands of clean, ambitious young fellows are constantly putting on the policeman’s uniform all over the country, and rising to places as detectives and officials. The manufacturer or merchant may find himself in the police commissioner’s chair. Even the suburbanite, with his bundles, may be, out at Lonesomehurst, a member of the village council, and thus responsible for the supervision of a police force that, though it be only two patrolmen and a chief, is important in its place. So in writing the story there has been an effort to show how a first-rate man like Commissioner Dougherty works. His methods are plain business methods. Most of his life he has earned his living following the policeman’s trade as a commercial business. What he did in a case of this kind, and how, and why, are matters of general interest and importance.

Finally, the story throws some useful light on criminals. It shows the cunning of the underworld, and also its limitations. To free the law-abiding mind of romantic notions about the criminal, and show him as he is, is highly important in the prevention of crime.