“Have to do, I suppose,” Shelley grumbled. “One of these days, Cunningham, I am going to get a decent job, where I don’t have to miss sleep. Thank Heaven I’m not married, anyway. What does your wife think of your spending so much time away from home?” Then, without waiting for a reply to this purely rhetorical question, he swept on: “Anyhow, we must try to get a spot of sleep in the train if we can. I guess we shan’t get much tomorrow.”

Cunningham made for the door and hurried out, preparing to get the car which he knew would be demanded to get them to St. Pancras.

Shelley followed in more leisurely fashion, stopping at the finger-print department to get a photograph, now developed, fixed, and dried, of the prints of J. K. Wallace, the ex-criminal who had so mysteriously appeared in this case at such a late stage, and whom, even yet, they were totally unable to identify.

At the door of the car he was stopped by an excited figure, bowler hat all awry, pince-nez absurdly on the tip of his nose.

“Hullo, Mr. Fairhurst,” he said. “Sorry I can’t stop now. In a hurry. We’re on the track of Miss Arnell, and we have to catch a train.”

“But, Mr. Shelley,” panted the little man, who had obviously been hurrying, “I want to talk to you about this case.”

“Sorry, Mr. Fairhurst,” snapped Shelley. “Any other time. At the moment I’m busy.”

“It is important!”

“Sure?”

“Yes, Mr. Shelley.”

Shelley paused for a moment, thinking of some way out of this difficulty. True, Fairhurst had brought them information of some importance previously, and it was possible that he had some sort of material clue which he was now trying to put before them. Then he saw the solution.

“If you think this information is vital, Mr. Fairhurst,” he said, “jump in.” He indicated the waiting car, at the wheel of which a policeman sat impassively.

“Come with you?” Mr. Fairhurst was very excited at the prospect.

“If you think you can be any help to us in this case.” Shelley was carefully non-committal.

“Yes!” Mr. Fairhurst’s eyes shone, his pince-nez slipped a degree nearer the tip of his nose, and the tilt of his hat became more unconsciously rakish than ever. “Yes!” he repeated. “I will come with you to wherever you are going, Mr. Shelley; and I hope that I may be of some assistance in bringing this rascal to heel.”

Speedily, silently, and efficiently the police car sped along the Strand, up deserted Kingsway, and so to St. Pancras. Soon they were comfortably tucked away in the seclusion of a first-class compartment; speeding through the sleeping suburbs towards the north.