Almost on the lip of the crater a large tank had come to a standstill. Two jagged holes in her fantastically-painted sides showed that a Hun anti-tank gun had scored direct hits, but whether these had put the mobile fort out of action Derek was unable to determine. While debating whether it would be safer to take cover under the lee of the tank or to remain in the doubtful security of a wide shell-crater, Daventry saw the door in the wake of the tank's sponson thrown open, and a couple of mechanics crawl through, followed by a waft of brownish smoke. At first sight the flying-officer imagined that the men were the sole survivors of the land-ship's crew, but he was mistaken. It was a case of engine failure that had brought the tank to a halt, and since the only means of "cranking-up" was performed from without, the mechanics were risking death in the open in a laudable effort to restart the motors. Even as the men strained frantically at the handle a shell burst within five yards of the tank. One of the mechanics, caught by the direct blast of the explosion, was wiped out of existence; the other, by one of those inexplicable freaks of fortune, escaped with only a slight shock. Although only a few inches from his luckless comrade he was evidently in the so-called safety-zone of explosion. Slightly dazed, and apparently oblivious of the fact that he had missed death by inches, he sweated at the cranking-handle in a vain attempt to overcome the compression. Acting purely upon impulse, and not taking into account the risk, Derek scrambled up the loose mound of earth, against which bullets were burying themselves with a succession of dull thuds. Then across the few yards of open ground he ran, and threw himself at the starting-gear. The mechanic took no notice of the new arrival. His whole mind was set upon his task. Even had Derek been a Boche it is doubtful whether the man would have given him a thought. "Hold out there, mate!" shouted the mechanic, without raising his head. Derek grasped the cranking-handle. The other, placing his foot upon the metal, brought his whole weight down. Over swung the crank, and with a thunderous roar the powerful motor fired--and continued to do so. Through the eddying fumes Daventry could discern the mechanic, with hunched shoulders, stumbling towards the still open door. "This is a stunt that will suit me," exclaimed the young officer. "A change is as good as a rest." The next thing he remembered was barking his shins on the sharp, metallic edge of the threshold. Then, coughing and spluttering in the petrol-laden fumes, he heard the door clang behind him. The interior of a tank was not strange to Derek. Several times previously he had gone for joy-rides in the land-ships, but now he was experiencing a novel sensation, that of being cooped up in a mobile armoured fort in action.