Six minutes out from Miranda, the leading half blossomed into a cluster of ten thousand relativistic bomblets—bursting forth as an expanding shroud which, by the time it reached this world 472 kilometers in diameter, would custom-fit its dimensions.

Ahead, just below the surface of Miranda’s ice fields, tanks of supercooled chemicals—millions of them—would soon be detecting anomalous emissions in the sky. The ship had no way of knowing whether or not the operators of the solar system’s largest astronomical observatory would have time to realize that the blue-shifting gamma ray sources were interstellar lances, or that they and their liquid telescope array were targets. The ship’s mind was certain that even if someone at the target did comprehend what was about to happen, he was already powerless to prevent it. Armed with this knowledge, and with indifference, the Intruder hurried on.

2

Miranda Station

The visiting scientists’ quarters were all full, making it necessary to put dividers into the already cramped staterooms to accommodate the seasonal influx of graduate students. Don Peterson’s room was one of the largest, but it was still scarcely larger than the average bathroom back home on Earth—a windowless cell with a sink, foldaway desktops, and a roll-down bed that left no space for a liquid crystal wallscreen.

But one luxury that Singapore’s Miranda Research Station did offer was a combination control van and community tearoom with panoramic views. The van was Peterson’s favorite place. Even though the view did not change appreciably day-to-day, he had never grown tired of it. Cut by the horizon, Uranus was a huge dome glowing with backscattered sunlight. The rocks outside cast long shadows over fields of dust and ice crystals, blue under the pale white stars.

Peterson liked the solitude of the graveyard shift. No one else had wanted it, but he had volunteered gladly, because it released him from the overcrowding of a dozen-member support crew and a scientific party of thirty. He also hoped to take advantage of a phenomenon no one had yet explained, but which had been confirmed by nearly a century of oceanic and space exploration—that most important discoveries tended to be made between midnight and 3:00 a.m.

Tonight, as he sipped a bulb of tea and scribbled notes on a liquid crystal pad, Peterson was keenly aware of the probability curve, and waited patiently for something interesting to emerge; but his fears that he would end his tour on Miranda without scoring any significant discoveries were wrongly placed. He was about to score far too many.

The first sign of the visitors was eighty gamma photons—each measuring exactly 0.5 million electron volts—passing through the observatory’s array of tanks and producing brief pulses of light that were measured and recorded by ultrasensitive photomultiplier cameras set on the tank walls. One ten-thousandth of a second after the first eighty photons struck, a small area of the station’s computer memory— the SETI file—was triggered in time to receive the next batch. By then, the SETI bank had programmed itself to respond only to the 0.5 million electron-volt gammas, ignoring all other particles passing through the detectors. In every tank, the cameras recorded gamma ray tracks through the fluids, revealing their energy levels and indicating precisely the direction from which they had entered.