They followed the _Dog Star_ for an entire space day, keeping the same distance between the ships. The craft was undoubtedly still heading for Earth and its company of artificial satellites. If her occupants had spotted the other ship, they did not seem alarmed. Kalmus appeared to be walking right into capture at a time when victory seemed to be completely his. It didn’t make sense. Hours later, Rock was interrupted from study of a sky chart when Shep cried out in an anguished voice. Rock dashed over to the port where his friend was looking out. “There’s been an explosion aboard the _Dog Star_!” Shep blurted. “A big burst of flame poured out of it!” “We’ve got to get to her right away!” Rock said hoarsely. It took some time to change course and swing around in pursuit of the _Dog Star_’s new glide path. Rock fretted impatiently. He had nightmare visions of what might have happened or might now be happening to his buddies aboard the stricken vessel. As soon as the _Northern Cross_ had matched flight paths with the other craft, Rock reduced their velocity so they could creep up on the _Dog Star_ “overhead.” The maneuver was accomplished as quickly as possible. The _Northern Cross_ now lay “above” the _Dog Star_, with a space of about a hundred feet between. Rock set the controls on hold positions as Shep procured a long towline. The boys dressed hurriedly in space gear, then opened the air lock closest to the ragged topside hole they had seen in the other ship. They secured the safety line to an outside anchor ring, then Rock fastened the line to his own suit. “Maybe you’d better stay out of this with that bad ankle of yours,” Rock told Shep. “And let you go across on your own?” Shep retorted. “No, I’m sticking with you this time.” Rock shoved off briskly from the ship’s hull and floated across the gulf of vacuum toward the _Dog Star_. He landed on the hull not far from the explosion hole that was amidships near a rocket-tube cluster. Shep pulled in the line and then launched himself across the emptiness. Rock steadied him as he landed. The two scrambled immediately down through the gaping cavity, careful not to snag their suits on the sharp edges. The boys climbed down along the bulkheads of the corridor where smoke swirled like fog. Reaching the floor, they were met by four running figures in space suits. The boys recognized Kalmus and his three companions in a desperate hurry. Rock lashed out boldly at Kalmus who was rushing at him. He heard the big fellow groan over his suit radio as the blow landed. But then Rock was charged by Jack Judas. He was lifted off the floor and, because of his helplessness when not in contact with it, was sent crashing heavily against the wall of the corridor.