For answer, a blinding ray of light, directed by a powerful pocket lamp, struck him full in the face, and before he realised what had happened, someone had leapt on to the wheel and was by his side, clutching at the rails on top of the van. Something cold and hard was pressed against his neck. “Utter a sound and you’re a dead man,” said a man’s voice. A quarter of an hour later, all that stood for authority in London was searching for a dark low motor car, and Peter Dawes, sitting on the edge of his bed in his pyjamas, was eagerly questioning one of his junior officers over the ’phone. “Robbed the mail? Impossible! How did it happen? Were they arrested? I’ll be with you in ten minutes.” He slipped into a suit, buttoned his mackintosh, and stepped out into the wild night. His flat was opposite a cab rank, and in less than ten minutes he was at Scotland Yard. “… the man said the thing was over so quickly he hadn’t a chance of shouting, besides which, the fellow who stood by his side threatened to shoot him.” “What have they taken?” “Only one bag, so far as can be ascertained. They knew just what they were after, and when they had got it they disappeared. The constable at the other end of the street heard the man shout, and came running down just in time to see a motor car turn the corner.” Later, Peter interviewed the driver, a badly scared man, in the stable-yard of the contractor who supplied the horses for the post office vans. The driver was a man who had been in the Government service for ten years, and had covered the route he was following that night--except that he had never previously taken the side street rendered necessary by the condition of the road--for the greater part of that time. “Did you see anybody else except the man who sat by your side and threatened you?” asked Peter. “Yes, sir,” replied the man. “I saw what I thought was a girl in a black oilskin; she passed round to the back of the van.” “Where is the van? Is it here?” asked the detective, and they showed him a small, four-wheeled vehicle, covered in at the top and with two doors which were fastened behind by a steel bar and padlocked. The padlock had been wrenched open, and the doors now stood ajar. “They had taken out the mail bags, sir, in order to sort them out to see what was gone.” Peter flashed his lamp in the interior, examining the floor and sides carefully. There was no clue of any kind until he began his inspection of the inside of the doors, and there, on the very centre, was the familiar label. “Four Square Jane, eh?” said Peter, and whistled. VII “I deeply regret that I found it necessary to interfere with His Majesty’s mails. In a certain bag was a letter which was very compromising to me, and it was necessary that I should recover it. I beg to enclose the remainder of the letters which are, as you will see, intact and untampered with!”