"You'll be wanted all right," replied the Inspector. "He's under remand at present, and I don't suppose the case will come on for another month. There are several pretty black marks against Master Dick, and we hope to collect enough evidence to put him out of business for some considerable period." He paused. "By the way," he added, "if you've a few minutes to spare, come along up to our place and let me introduce you to one or two of the boys. I told them what you did for us the other day, and they'd be glad of the chance of shaking hands with you." Knowing that Mark was unlikely to be free until four o'clock, Colin decided that he might as well accept the invitation. He had never been inside Scotland Yard, and the prospect rather appealed to him. "What shall I do with the car?" he asked. "Leave it here?" "Better bring it into the yard," said the Inspector. "No one will try to pinch it then--not unless he's a bit of an optimist." Getting into his seat, Colin started forward alongside his companion, and turned in through the big iron gates which guard the headquarters of the London Police Force. There were several other cars standing against the wall, and, leaving his own in company with them, he followed the Inspector through a low doorway and up a long flight of stone stairs. They emerged into a broad corridor with doors on either side. "Here we are!" announced his guide, halting in front of the second. "I don't know who's on duty to-day, but we're sure to find somebody about." He led the way into a large, business-like apartment, the principal furniture of which consisted of a couple of roll-top desks. At one of them was seated an alert-looking man in a well-cut blue suit, who glanced up sharply at their entrance. "Hullo, Pat!" said the Inspector. "I've got someone here I want to introduce you to. This is Doctor Gray of St. Christopher's Hospital." The other laid down his pen, and, rising from his chair, shook Colin's hand. "You're welcome, sir," he said, with a distinctly Irish accent. "We have heard all about you from our friend Marsden. My name is O'Brien--Inspector Patrick O'Brien. I am pleased to have the privilege of making your acquaintance." "It's very nice of you to put it like that," said Colin. "I don't think I deserve any particular compliments, though. I only did what any one else would have done who had happened to be on the spot." Both men smiled. "That may be your impression," was the answer, "but you can take it from me that you're a trifle off the mark. Watching a police officer kicked to death is one of the public's favourite entertainments."