Hunting the submarines was principally the job of the P-3C Orion. Each Orion carried sonobuoys, air-deployable active and passive sonar sets that were dropped from the belly of the aircraft. On detecting something, a sonobuoy reported to its mother aircraft and then automatically sank lest it fall into unfriendly hands. The sonobuoys had limited electrical power and thus limited range. Worse, their supply was finite. The sonobuoy inventory was already being depleted alarmingly, and soon they would have to cut back on expenditures. Additionally, each P-3C carried FLIRs, forward-looking infrared scanners, to identify the heat signature of a nuclear sub, and MADs, magnetic anomaly detectors that located the disturbance in the earth's magnetic field caused by a large chunk of ferrous metal like a submarine. MAD gear could only detect a magnetic disturbance six hundred yards to the left and right of an aircraft's course track, and to do this the aircraft had to fly low, consuming fuel and limiting the crew's visual search range. FLIR had roughly the same limitation.

Thus the technology used to localize a target first detected by SOSUS, or to "delouse" a discrete piece of ocean preparatory to the passage of a convoy, simply was not up to a random search of the deep ocean.

Quentin leaned forward. A circle had just changed to a dot. A P-3C had just dropped an explosive sounding charge and localized an Echo-class attack sub five hundred miles south of the Grand Banks. For an hour they had a near-certain shooting solution on that Echo; her name was written on the Orion's Mark 46 ASW torpedoes.

Quentin sipped at his coffee. His stomach rebelled at the additional caffeine, remembering the abuse of four months of hellish chemotherapy. If there were to be a war, this was one way it might start. All at once, their submarines would stop, perhaps just like this. Not sneaking to kill convoys in midocean but attacking them closer to shore, the way the Germans had done . . . and all the American sensors would be in the wrong place. Once stopped the dots would grow to circles, ever wider, making the task of finding the subs all the more difficult. Their engines quiet, the boats would be invisible traps for the passing merchant vessels and warships racing to bring life-saving supplies to the men in Europe. Submarines were like cancer. Just like the disease that he had only barely defeated. The invisible, malignant vessels would find a place, stop to infect it, and on his screen the malignancies would grow until they were attacked by the aircraft he controlled from this room. But he could not attack them now. Only watch.

"PK EST 1 HOUR—RUN," he typed into his computer console.

"23," the computer answered at once.