Clenching his leather-gloved hand the A.P. let out with his left. His fist, taking the lurcher fairly on the point of the nose, sent the animal reeling. The respite was but momentary. Like a dart the dog flew straight for the young officer's throat. Kirkwood met the animal as it leapt in midair. His right hand, with its protection of the undressed leather gripped the lurcher round the muzzle, his fingers and thumb meeting inside the brute's wide-open jaws. Instantly the A.P.'s left hand grasped the dog's lower jaw. So far so good. The animal, unable to bite, attempted to shake himself clear. Foiled in this direction he planted his hind legs firmly in the ground and, giving his body a series of jerks, sought to pull the A.P. off his balance. "Shoot the brute!" exclaimed Barcroft from above. "Risk it! It can't be helped. Clap the muzzle close to the brute's hide." But Bobby thought otherwise. Even if he could afford the risk of letting go the dog's jaws with one hand and draw his revolver the muffled report would still be sufficiently audible to alarm the Huns. For perhaps half a minute he stood his ground, contenting himself by prising the lurcher's jaws apart. Then, slowly at first, he began to bend the animal's head backwards. It was a horrible yet necessary task--one that taxed the A.P.'s strength and endurance to the uttermost. Already he could feel the dog's teeth penetrating the gloves, and those saliva-streaming fangs meant trouble once they pierced the flesh. Yet the man was winning through. Back and back he levered the animal's head. The brute's breath was coming in short, irregular pants; its blood-flecked eyes were almost bursting from their sockets. Still it struggled furiously, striving in vain to break away from the A.P.'s vice-like grip. "By Jove! He'll never do it," thought Barcroft. "The brute's tiring him out." At the risk of barked shins and elbows the flight-sub descended from his perch. Gaining the ground he drew his revolver, wrapped his scarf several times round the weapon to muffle the sound of the explosion, and cautiously approached the combatants. Extreme care was necessary, for the lurcher, driven to desperation, was turning his antagonist round and round. Kirkwood, his whole energies devoted to twisting the animal's neck, was unable to counteract the dog's movements, nor did the animal remain sufficiently still to enable Barcroft to plant the muzzle of his weapon firmly against its ribs. The end came with unexpected suddenness. With a distinctly audible crash the lurcher's vertebra snapped. Its body seemed instantly to grow limp. The sudden cessation of resistance caused Kirkwood to fall forward across the still quivering body of his enemy. Barcroft lifted his chum and set him on his feet. The A.P., now the duel with death was done, was as pale as a sheet and trembling in every limb. "I'll be all right in a minute," he gasped. "Feel as ill as a seasick cat."