The patrol pattern had been set in the mission briefing. The four boomers had thirty-mile sectors, and each sector was divided into three ten-mile segments. Each boat could patrol in the center slot, leaving the north and south slots empty for everything but weapons. The patrol patterns were left to the judgment of individual skippers, but they worked out the same way. Pennsylvania was on a northerly course, trolling along at a mere five knots, just as she'd done for her now-ended deterrence patrols carrying Trident missiles.

She was making so little noise that a whale might have come close to a collision, if it were the right time for whales in this part of the Pacific, which it wasn't. Behind her, at the end of a lengthy cable, was her towed-array sonar, and the two-hour north-south cycle allowed it to trail straight out in a line, with about ten minutes or so required for the turns at the end of the cycles to get it straight again for maximum performance.

Pennsylvania was at six hundred feet, the ideal sonar depth given today's water conditions. It was just sunset up on the roof when the first trace appeared on her sonar screens. It started as a series of dots, yellow on the video screen, trickling down slowly with time, and shifting a little to the south in bearing, but not much. Probably, the lead sonarman thought, the target had been running on battery for the past few hours, else he would have caught the louder signals of the diesels used to charge them, but there the contact was, on the expected 60Hz line. He reported the contact data to the fire-control tracking party.

Wasn't this something, the sonarman thought. He'd spent his entire career in missile boats, so often tracking contacts which his submarine would maneuver to avoid, even though the boomer fleet prided itself on having the best torpedomen in the fleet. Pennsylvania carried only fifteen weapons aboard—there was a shortage of the newest version of the ADCAP torpedo, and it had been decided not to bother carrying anything less capable under the circumstances. It also had three other torpedolike units, called LEMOSSs, for Long-Endurance Mobile Submarine Simulator. The skipper, another lifelong boomer sailor, had briefed the crew on his intended method of attack, and everyone aboard approved. The mission, in fact, was just about ideal. The Japanese had to move through their line. Then operational pattern was such that for them to pass undetected through the line of battle, as the skipper had taken to calling it, was most unlikely.

"Now hear this," the Captain said over the 1-MC announcing system. Every speaker had been turned down, so that the announcement came as a whisper that the men strained to hear. "We have a probable submerged contact in our kill zone. I am going to conduct the attack just as we briefed it. Battle stations," he concluded in the voice of a man ordering breakfast at HoJo's.