Resurgence by Charles Sheffield

to decipher their records. They came here to seek our advice and our assistance, although there is no suggestion that they ever thought the trip would prove fatal to them. They call themselves by a name which our translation machines offer as Marglotta . Their home world is in the Sag Arm, and it translates as Marglot. It is somewhere in here."
    Graves again gestured, and the Gulf with its pattern of Bose nodes vanished. It was replaced in the 3-D display by a long, twisting volume of space, dotted with the beacons of supergiant stars and great obscuring clouds of dust and gas.
    "The Sag Arm, in detail. Here"—a blinking point of blue appeared—"is our best estimate for the location of the Marglot system. Either we are misunderstanding their records, or the Marglotta come from a strange world indeed. There seem to be four poles, defined as North, South, Hot, and Cold. No explanation is offered for this. The Marglotta apparently did not feel it necessary to keep in their files descriptive details of their own home world. However, you will have plenty of time to puzzle out the significance of the four planetary poles later."
    Later? But if no one else asked the question, Darya was not about to interrupt. The councilor's big, domed head, with its powerful mnemonic twin memory and misty blue eyes, still had the power to intimidate her.
    Graves went on, "Now for a question which you may already have asked yourselves. Why was I, a member of the inter-clade Ethical Council, called in? I have perhaps had more contact than other councilors with Builder artifacts, but I am by no means an expert on the subject. How are ethics involved? I can give you a simple answer. We may be dealing with attempted genocide. The Marglotta say that their world is changing. Some great destructive force is at work in the Sag Arm. It has spread steadily for many millennia, possibly for millions of years. The Marglotta suspect the influence of the Builders. I cannot speak as to the truth of that conjecture, but we have made our own observations of the Sag Arm. We find a region utterly lacking in light and life. Observe."
    The chamber dimmed. The new 3-D display seemed to grin back at Darya. It was as though something had taken a bite out of the spiral arm and left a small sphere of black nothing where stars should be.
    "Scary picture." Louis Nenda spoke softly, as much to himself as to Darya. "And hard luck on Marglotta and friends."
    She whispered back, "Scary, and strange. Anything on that scale has to be Builder activity. But no Builder artifact in our arm ever destroyed whole stellar systems."
    Julian Graves was staring at them. Louis Nenda said, more loudly, "Somethin's doing a number on the Sag Arm. But Councilor, it's a zillion lightyears away. We're safe enough."
    "I do not share your confidence on the latter point." Julian Graves's deep voice filled the hall. "Our own clades— all our own clades—could be in danger. We went back to observations of the Sag Arm made millennia ago. The dark sphere is growing, and as it spreads, its outer boundary will come closer to an edge of the Sag Arm—to the place, in fact, where nodes of the Bose network stretch across the Gulf toward our own spiral arm."
    Darya could sense Hans Rebka moving restlessly at her side. He said, "I see what you're getting at. But what are we talking about here? We sure don't need to worry about next week, or next year. How long do we have?"
    "Precisely?" The lights came on, and Graves was frowning. "I do not know. E. Crimson Tally? An estimate?"
    "From the data available, the affected area could reach the far edge of the Gulf somewhere between twenty-nine and thirty-two thousand years from now."
    Graves nodded. "There's your answer, Captain Rebka. But I wonder why you ask."
    Rebka stood up restlessly, although squeezed between Darya and E.C. Tally he had no place to go. "Because of who I am, and what I've done all my life. I can see why Darya might get excited when there are