Going from the Old Bailey not long since, at the conclusion of a murder trial, I got to Farringdon Street just as a train was starting, and scrambled into a third-class carriage. It was nearly full, and I took the last seat. Instantly I recognized two of my fellow-travellers. They were an elderly woman and a young woman, both dressed in deep black.

No one took any notice of them. But what objects of interest they would have been to the other passengers had the identity of one of them been known!

She was the affianced wife of a young man who had that day been condemned to death for the barbarous murder of the woman to whom he was already married. The girl who was sitting with her mother in the crowded compartment on the Metropolitan Railway had just parted with the man who had murdered another woman to make her his wife, and had that day been sent to the gallows.

I had heard this poor girl on the previous day tell in the crowded court one of the strangest incidents of the tragedy. When all London was ringing with the mystery of the murder, her affianced husband came to tea with her people. The talk turned upon the startling crime, and everybody present said they hoped the murderer would soon be discovered. And all the time the murderer was sitting at the tea-table, the honoured guest of that happy little family party!

It is because its mystery has fascinated me from the beginning, and because the spell has never been weakened, that I have wandered London in every direction night and day in a ceaseless endeavour to know it in every phase and form. In these years of wandering, often far off the beaten track, I have learnt much that is not common knowledge, and every day I am learning more. If I were to say that London has laid its heart bare to me it would be untrue, for that has happened to no man. Many of its inner workings are mysteries even to those whose task in life it is to solve them.

But I have penetrated far enough to be able to act as guide to those who have no opportunity of making the journey by themselves, who, even if they had, would make it with small profit to their knowledge of facts.

For the truth does not lie in the open road, and to take the narrow winding way that leads to it, one must be armed with two things—the word that will carry you past the vigilant sentinels and the knowledge that will insure your safe return.

I have said so much that the reader who wishes to accompany me in these journeys in search of the mysterious side of London life may know over what ground we shall have to travel But I should like to say one word more. We shall not need police escort or protection. My obligation to the police is great for many kindly services rendered, and I have the sincerest admiration for the patience and the energy with which they guard the capital's wealth and the lives of its citizens, but I have never asked for their assistance in my journeyings into dark places. The police are known, and in their presence the tongue of the local gossip is tied, and the intentions of the person accompanying them are suspected.

Wherever I have gone it has always been alone or with someone whom the inhabitants of the area—whether honest or criminal, toilers or idlers, decent folk or outcasts—have always regarded with a friendly eye.

Often a journey has been made alone. It has been made by day and by night, and though there have been times when I have been glad to see the beaten track and the lights and the traffic again, I have never received either insult or injury. And I have Been in spots that are officially recognized as the most dangerous in London.