It was a case of fight like the devil and trust to luck and the darkness for aid.
Almost before they knew it, they had broken through the trio in front of them and had turned down the Calles Ancha, running in a form that would have done credit to a college track team. Behind them they heard the muffled oaths of their pursuers as they fell over the party they had just left.
"They don't want to attract the police any more than we do," gasped Dawson. "They don't dare shoot!"
But as he spoke there came the z-z-i-pp of a bullet, accompanied by the sharp crack of a revolver somewhere behind them.
"Careful," warned Stewart. "We've got to skirt that street light ahead. Duck and – "
But with that he crumpled up, a bullet through his hip.
Without an instant's hesitation Dawson stooped, swung his companion over his shoulder, and staggered on, his right hand groping for his automatic. Once out of the glare of the arc light, he felt that he would be safe, at least for a moment.
Then, clattering toward them, he heard a sound that spelled safety – one of the open nighthawk cabs that prowl around the streets of the Mexican capital.
Shifting Stewart so that his feet rested on the ground, he wheeled and raked the street behind him with a fusillade from his automatic. There was only a dull mass of whitish clothing some fifty yards away at which to aim, but he knew that the counter-attack would probably gain a few precious seconds of time – time sufficient to stop the cab and to put his plan into operation.
The moment the cab came into the circle of light from the street lamp Dawson dragged his companion toward it, seized the horse's bridle with his free hand and ordered the driver to halt.
Before the cabby had recovered his wits the two Americans were in the vehicle and Dawson had his revolver pressed none too gently into the small of the driver's back. The weapon was empty, but the Mexican didn't know that, and he responded instantly to Dawson's order to turn around and drive "as if seventy devils of Hades were after him!"
Outside of a few stray shots that followed as they disappeared up the street, the drive to the Embassy was uneventful, and, once under the shelter of the American flag, the rest was easy.
Stewart, it developed, had sustained only a flesh wound through the muscles of his hip – painful, but not dangerous. Within ten minutes after he had reached O'Shaughnessy's office he was dictating a code wire to Washington – a cable which stated that a vessel with a Spanish name, commencing with something that sounded like "Eep," had cleared Hamburg on the seventh, loaded with arms and ammunition destined to advance the interests of Mexican revolutionists and to hamper the efforts of the United States to preserve order south of the border.
The wire reached Washington at noon of the following day and was instantly transmitted to Berlin, with instructions to Ambassador Gerard to look into the matter and report immediately.
Vessel in question is probably the Ypiranga [stated a code the following morning]. Cleared Hamburg on date mentioned, presumably loaded with grain. Rumors here of large shipment of arms to some Latin American republic. Practically certain that Wilhelmstrasse is behind the move, but impossible to obtain confirmation. Motive unknown.
Ten minutes after this message had been decoded the newspaper correspondents at the White House noted that a special Cabinet meeting had been called, but no announcement was made of its purpose or of the business transacted, beyond the admission that "the insult to the flag at Tampico had been considered."
Promptly at noon the great wireless station at Arlington flashed a message to Admiral Mayo, in command of the squadron off the Mexican coast. In effect, it read:
Proceed immediately to Vera Cruz. Await arrival of steamer Ypiranga, loaded with arms. Prevent landing at any cost. Blockade upon pretext of recent insult to flag. Atlantic Fleet ordered to your support.
"The rest of the story," concluded Quinn, "is a matter of history. How the fleet bottled up the harbor at Vera Cruz, how it was forced to send a landing party ashore under fire, and how seventeen American sailors lost their lives during the guerrilla attack which followed. All that was spread across the front pages of American papers in big black type – but the fact that a steamer named the Ypiranga had been held up by the American fleet and forced to anchor at a safe distance offshore, under the guns of the flagship, was given little space. Apparently it was a minor incident – but in reality it was the crux of the whole situation, an indication of Germany's rancor, which was to burst its bounds before four months had passed, another case in which the arm of Uncle Sam had been long enough to stretch halfway across a continent and nip impending disaster."
"But," I inquired, as he paused, "what became of Dawson and Stewart?"
"That I don't know," replied Quinn. "The last time I heard of Jack he had a captain's commission in France and was following up his feud with the Hun that started in Mexico City four months before the rest of the world dreamed of war. Dawson, I believe, is still in the Department, and rendered valuable assistance in combating German propaganda in Chile and Peru. He'll probably be rewarded with a consular job in some out-of-the-way hole, for, now that the war is over, the organization to which he belongs will gradually dwindle to its previous small proportions.
"Strange, wasn't it, how that pair stumbled across one of the first tentacles of the World War in front of a café in Mexico City? That's one beauty of government detective work – you never know when the monotony is going to be blown wide open by the biggest thing you ever happened upon.
"There was little Mary McNilless, who turned up the clue which prevented an explosion, compared to which the Black Tom affair would have been a Sunday-school party. She never dreamed that she would prevent the loss of millions of dollars' worth of property and at least a score of lives, but she did – without moving from her desk."
"How?" I asked.
But Quinn yawned, looked at his watch, and said: "That's entirely too long a story to spin right now. It's past my bedtime, and Mrs. Quinn's likely to be fussy if I'm not home by twelve at least. She says that now I have an office job she can at least count on my being round to guard the house – something that she never could do before. So let's leave Mary for another time. Goodnight" – and he was off.
IV
THE CLUE ON SHELF 45
"Of course, it is possible that patriotism might have prompted Mary McNilless to locate the clue which prevented an explosion that would have seriously hampered the munitions industry of the United States – but the fact remains that she did it principally because she was in love with Dick Walters, and Dick happened to be in the Secret Service. It was one case where Cupid scored over Mars."
Bill Quinn eased the game leg which he won as the trophy of a counterfeiting raid some years before into a more comfortable position, reached for his pipe and tobacco pouch, and settled himself for another reminiscence of the Service with which he had formerly been actively connected.
"Mary was – and doubtless still is – one of those red-headed, blue-eyed Irish beauties whom nature has peppered with just enough freckles to make them alluring, evidences that the sun itself couldn't help kissing her. But, from all I've been able to gather, the sun was in a class by itself. Until Dick Walters came upon the scene, Miss McNilless held herself strictly aloof from masculine company and much preferred to spend an evening with her books than to take a trip to Coney or any of the other resorts where a girl's kisses pass as current coin in payment for three or four hours' outing.
"Dick was just the kind of chap that would have appealed to Mary, or to 'most any other girl, for that matter. Maybe you remember him. He used to be at the White House during Taft's regime, but they shifted most of the force soon after Wilson came in and Dick was sent out to