He strapped his leg in place and uncapped one of the tubes and applied a thin bead of the gel to the mortar seam between two of the cinder blocks nearest the floor.

All manner of horrible thoughts flashed through Cabrillo’s mind when the gel didn’t react as it had when they were experimenting back on the Oregon. But the brain can think up scary scenarios in fractions of seconds. The chemical reaction was a tad slower.

Stone and Murph had deduced the chemical makeup of the mortar used here by reading through thousands of pages of declassified documents in Archangel, where the company that had built the facility back in the ’70s was located. (In truth, a team from the Oregon had broken into the facility and scanned the documents over a three-night period and fed them into the ship’s mainframe computer for translation, and then Eric and Mark had gotten to work.)

In less than a minute, the acidic putty had completely broken down the mortar. Cabrillo then attached a probe to the tube, so he could stick it into the narrow slit he’d created, and applied more gel to etch away the remaining mortar on the far side of the block. When he was certain it was clear, he kicked the block into a narrow crawl space between his cell’s wall and the prison’s exterior basement wall. He peered into the gloomy space and saw that the next obstacle was a preformed slab of concrete resting on poured-cement footings. Each section probably weighed ten or so tons.

The mortar acid wouldn’t work on it, but the pack of C-4 plastic explosives would more than do the job.

Chapter Two

It took Cabrillo nearly an hour to enlarge his one-block hole into an aperture he could crawl through. On the off chance of a random inspection through the peephole, he stacked the blocks in front of it with just enough room to squeeze behind. In the cell’s dismal lighting it would give the optical illusion of a solid wall.

Next, he attacked the wall next to the cell door. Rather than use the acidic putty to remove individual blocks, he first eroded all the mortar he could reach in an area just wider than his body. Again, this was a precaution in case a guard or the warden came around. Only when he was ready to make his move would he blow through the rest of the mortar.

The second-to-last item in his prosthetic limb had been a tiny transmitter. Once he hit the button and its burst signal was sent to the men waiting on the ship, he had six minutes to get the man he had come here to rescue, blow the C-4 he’d already planted, and make it up to the surface.