The observers aboard J5 gasped as the picture being transmitted from J4 appeared on the screen. Vegas, the only ships intended for fight through planetary atmospheres, were the only UNSA vessels in the vicinity that were constructed to a streamlined design; this ship was clearly not a Vega. Those sweeping lines and delicately curved, gracefully balanced fins had not been conceived by any designer of Earth.

Some of the color drained from Hayter's face as he stared incredulously at the screen and the full implications of the sight dawned on him. He swallowed hard, then surveyed the astounded faces surrounding him.

"Man all stations on the command floor," he ordered in a voice approaching a whisper. "Summon the mission director to the bridge immediately."

Chapter Four

Framed in the large wall display screen on the bridge of Jupiter Five , the alien craft hung in a void against a background of stars turning almost imperceptibly. It was almost an hour since the new arrival had slowed down to rest relative to the command ship and had gone into a parallel orbit over Ganymede. The two ships were standing just over five miles apart and every detail of the craft was now easily discernible. There was little to interrupt the sleek contours of its hull and fin surfaces and no identification markings or insignia of any kind. There were, however, several patches of discoloration that might have been the remnants of markings which had been abraded, or perhaps, scorched. In fact the whole appearance of the craft somehow gave the impression of wear and deterioration suffered in the course of a long, hard voyage. Its outer skin was rough and pitted and was from end to end disfigured by indistinct streaks and blotches, as if the whole ship had at some time been exposed to severe heat.

Jupiter Five had been the scene of frenzied activity ever since the first meaningful pictures came in. There had been no indication so far of whether or not the craft carried a crew or, if it did, what the intentions of that crew might be. Jupiter Five carried no weapons or defensive equipment of any kind; this was one eventuality the mission planners had not considered seriously.

Every position on the command floor was now manned and throughout the ship every crew member was at his assigned emergency station. All bulkheads had been closed and the main drives brought to a state of standby readiness. Communications with the bases on the surface of Ganymede and from other UNSA ships in the vicinity had ceased, in order to avoid revealing their existence and their locations. Those daughter ships of J5 capable of being made flight-ready within the time available had dispersed into the surrounding volume of space; a few were under remote control from J5 , to be used as ramships if necessary. Signals beamed at the alien craft evoked a response, but J5's computers were unable to decode it into anything intelligible. Now there was nothing else to do but wait.

Throughout all the excitement, Hunt and Danchekker had stood virtually dumbstruck. They were the only people present on the bridge who were privileged to enjoy a grandstand view of everything that happened, without the distraction of defined duties to perform. They were, perhaps, the only ones able to reflect deeply on the significance of the events that were unfolding.

After the discoveries of first the Lunarians and then the Ganymeans, the notion that other races besides Man had evolved to an advanced technological level was firmly accepted. But this was something different. Just five miles away from them was not some leftover relic from another age or the hulk of an ancient mishap. There was a functional, working machine that had come from another world. Right at that moment, it was under the control and guidance of some form of intelligence; it had been maneuvered surely and unhesitatingly to its present orbit and it had responded promptly to J5's signals. Whether it contained occupants or not, these events added up to the first-ever interaction between modern Man and an intelligence that was not of his planet. The moment was unique; however long history might continue to unfold, it could never be repeated.

Shannon stood in the center of the bridge gazing up at the main screen. Hayter was standing beside him, running his eye over the data reports and other images being presented on the row of auxiliary screens below it. One of them showed a view of Gordon Storrel, the deputy mission director, standing by in the emergency command center with his own staff of officers. The outgoing signal to Earth was still operating, carrying complete details of everything that happened.

"Analyzers have just detected a new component," the communications officer called out from his station on one side of the bridge. Then he announced a change in the pattern of signals being picked up from the alien craft. "Tight-beam transmission resembling K-Band radar. PRF twenty-two point three four gigahertz. Unmodulated."

Another minute or so dragged endlessly by. Then, another voice: "New radar contact. Small object has separated from alien ship. Closing on J5. Ship maintaining position."

A wave of alarm, felt rather than sensed directly, swept over the observers on the bridge. If the object was a missile there was little that they could do; the nearest ramship was fifty miles away and would require half a minute, even under maximum acceleration, to intercept. Captain Hayter did not have time to juggle with arithmetic.

"Fire Ram One and engage," he snapped.

A second later the reply came to confirm. "Ram One fired. Locked on target."

Beads of perspiration showed on some of the faces staring at the screens. The main display had not yet resolved the object, but one of the auxiliary screens displayed a plot of the two large vessels and a small but unmistakable blip beginning to close the gap between them.

"Radar reports steady approach speed of ninety feet per second."

"Ram One closing. Impact at twenty-five seconds."

Shannon licked his dry lips as he scanned the data on the screens and digested the flow of reports. Hayter had done the right thing and placed the safety of his ship above all other considerations. What to do now was a problem that lay solely with the mission director.

"Thirty miles. Fifteen seconds to impact."

"Object holding course and speed steady."

"That's no missile," Shannon said in a tone that was decisive and final. "Captain, call off the interception."

"Abort Ram One ," Hayter ordered.

"Ram One disengaged and turning away."

Long exhalations of breath and sudden relaxing of postures signaled the release of the tensions that had been building up. The Vega streaking in from deep-space made a shallow turn that took it into a pass at twenty miles' distance and vanished once more into the infinite cosmic backdrop.

Hunt turned to Danchekker, talking in a low voice, "You know, Chris, it's a funny thing. . . . I've got an uncle who lives in Africa. He says there are some places where it's customary to greet strangers by intimidating them with screams and shouts and brandishings of spears. It's the accepted way of establishing your status."

"Perhaps they regard that as no more than a sensible precaution," Danchekker said drily.

At last the optical cameras distinguished a bright speck in the middle-distance between J5 and the alien ship. A zoom-in revealed it to be a smooth, silver disk devoid of any appendages; as before, the view gave no clue of its true shape. It continued its unhurried pace until it was a half-mile from the command ship; there it came to rest and turned itself broadside-on to present a simple, unadorned egg-shaped profile. It was just over thirty feet long and appeared to be of entirely metallic construction. After a few seconds it began showing a bright and slowly flashing white light.