Through the void at the heart of the Ring he could see blue-shifted starlight muddled, stirred. Here the wave functions were tangled, twisted, broken; here space was folded up like cheap cloth.

This distortion was the purpose of the Ring: this was the Kerr-metric Interface, a route to other universes -- the gateway through which the Xeelee had made their escape.

...Ghostly flocks slid through the tangled cosmic string net that made up the Ring.

Paul widened his perception to embrace the entire Ring. Everywhere the photino birds soared, silent and purposeful. Somehow the great artifact seemed helpless, and Paul felt an absurd impulse to hurl himself forward, to try to protect the glorious baryonic monument.

At length the photino birds appeared to come to a decision. A knot of birds, billions of them, formed around one section of the toroid -- perhaps some weak point -- and from all around the Ring more bird flocks flickered in short hyperdrive hops to join the growing throng. Soon only a few scouts were left near outlying parts of the Ring, and around the weak point there was a swarm of shadow birds so thick they obscured the Ring itself.

Cautiously Paul slid his awareness focus closer to the stricken region. The photino birds, he realized, were now passing into the structure of the cosmic string itself.

If cosmic string self-intersected it cut itself. A new subloop formed, budding off the old. And perhaps that subloop, too, would self-intersect, and split into still smaller loops... and so on.

Paul understood. It would be an exponential decay process, once started. And so the birds, concentrating their mass, deflected the passage of string loops, causing them to self-intersect. Soon, threads -- fragments of string thousands of miles long -- drifted out of the structure, passing unimpeded through the ranks of birds.

Soon the ghost-gray birds were jostling in their eagerness to breach the threads; and, within minutes, a slice through the Ring -- extremely thin, no more than a light year wide -- began to turn a dull yellow.

The photino birds were cutting the Ring, Paul realized uneasily, and it didn't appear that it would take them very long. And his little band of humans was still hours away.

He swept over the plain of the Ring and studied the turbulent space at its center. Thanks to the activities of the photino birds the Kerr-metric zone was like a pond into which gravel was being thrown. Star images rippled, and the inter-universal surface was awash with a milky blue light. Already the access paths through the zone must be disrupted--

-- and a shock wave of gravitational radiation burst over him.