Dimly, in the distance, he heard the beginning thunder of sound. It was something like the vague roar of a starting avalanche, a rumble, a mutter, a dim murmur growing louder. The smoke was too thick for him to see what was happening.
The murmur grew in volume. It became as loud as the roar of a tornado. The Ogrum stared toward it, trying to understand what it was. They were getting nervous, now. A few of them had started to run.
Something came through the smoke. It came in a lumbering gallop, a huge and terribly frightened beast. It saw the fires in front of it. Screaming it tried to turn back. The pressure of the horde behind carried it along.
A confused mass of dark bodies poured into the city. There were hundreds of them, thousands of them. Scared to the point of madness their one thought was how to escape. The smallest of them weighed more than two tons.
Craig, fighting against the effect of the gas, sobbed in sudden relief.
"Michaelson," he whispered. "You got there in time. You did it! You did it—"
Phase four of the attack plan had come into operation. Phase four called for Guru and the scientist to go around the edges of the vast swamp and set it on fire. Part of the swamp foliage would not burn under any circumstances. But great areas of dry reeds would burn like tinder.
The dinosaurs would run from the fires. The blazes would be set so the great monsters would have to flee toward the city. At the proper moment, the wall the Ogrum had built to keep them from the city would be blown up.
The dinosaurs would stampede across the city.
Craig remembered reading of the stampede of the long-horn cattle in the early days of the American west. Thousands of cattle, running madly, shook the earth with the thunder of their hooves, destroyed everything that stood in their way.