Glass hunched over the chart, across the table from Jerry Perez. The navigator looked up at Glass. “This is going to a little dicey, Skipper. It would sure be a lot safer if we could move out in the channel a little more.”

“Sorry, Jerry. We need the protection. You’ll have to trust the ESGN and the fathometer.”

The Electro-Stabilized Gyroscopic Navigation System was a marvel of modern engineering. A tiny beryllium ball hung in a near perfect vacuum, suspended by a powerful magnetic field. The same field caused the ball to rotate at over thirty thousand revolutions per second. At that high speed, the ball acted like an extremely sensitive gyroscope. It sensed and acted against every force that caused it, and Toledo, to move. Tiny, very sensitive accelerometers detected the gyroscope’s actions. The ESGN’s computer controller knew its initial position. By continuously adding the accelerometer’s output, the computer could tell Perez where they were within a few yards. The whole apparatus, hanging in the overhead just outside the radio room door, was the size of a bushel basket.

The problem with the whole scheme was in the accuracy of the initial position. Any error, even if it was off a few inches, was compounded geometrically as time passed and the mistakes accumulated. Even with GPS, the errors could add up. Normally Perez accounted for these errors by putting an “uncertainty” circle around the sub. He knew they were inside that circle. He just wasn’t sure where.

Now Glass was telling Perez to guide Toledo without benefit of that uncertainty circle. It was a tremendous risk. If he was wrong, even by a little bit, they could smash into the unforgiving granite wall. The fathometer didn’t help. It kept them off the bottom. It didn’t show them anything about the cliff that was so close by their port side.

The navigator nodded. Sweat poured off his forehead and trickled down his back. His hand shook as he grabbed a pair of dividers to measure their speed of advance.

“Yes, sir. I’ll do my best. Time for the turn. Recommended course one-seven-three, speed one-third. Thirty-two minutes on this leg.”

“Left full rudder,” Glass ordered. “Steady course one-seven-three.”

The rudder swung over, pushing the submarine’s nose around until she was pointed into the mouth of the fjord. Perez plotted the ESGN position as they steadied up on the new course. “Captain, hold us on track. The turn looked good.”

Glass had already moved forward. He stopped next to Brian Edwards. The XO stood beside the fire control system, watching as his team probed the dark, cold waters to find any threat. Edwards was scribbling on a notepad and talking on a set of sound-powered phones while he watched the computer screens.

“Got anything of interest, XO?” Glass asked him.