Strangers

high-velocity, steel-jacketed tear-gas shell that could penetrate most wooden doors or punch through a boarded window. When Jack fired, the shell smashed through the truck's grille into the engine compartment. A noxious yellow vapor began roiling into the cab by way of its ventilation system.
        The guards had been trained to remain in their secure roost in a crisis, for the cab had steel doors and bulletproof glass. But when they switched off the heater and closed the vents too late, they found themselves choking in the gas-filled cabin. They opened their locked doors, spilled out into the cold winter night, wheezing, coughing'
        In spite of the blinding, suffocating gas, the driver had drawn his revolver. Dropping to his knees, gagging, he squinted his copiously watering eyes in search of a target.
        But Jack kicked the gun out of his hand, grabbed him by the coat, and dragged him to the front of the truck, where he handcuffed him to a support strut on the bumper.
        After firing the shot that disabled the truck, Branch Pollard had sprinted down the knoll. Now, at the other end of the front bumper, he handcuffed the other protesting guard to another strut.
        Both guards were blinking furiously, trying to clear their gas-blurred vision to get a look at their attackers' faces, but that was wasted effort because Jack, Pollard, and Zepp were wearing ski masks.
        Leaving the securely shackled men, Jack and Pollard ran to the back of the truck, moving fast, though not because they feared being seen by other traffic on that lonely road. No traffic would pass until they were gone. The moment the Guardmaster unit had entered the flats, the last two members of the robbery team, Hart and Dodd, had sealed off both ends of the road with stolen vans that had been repainted and equipped with Department of Highway signs. Against an impressive backdrop of emergency beacons flashing on the roofs of their vans and on sawhorses they had set out on the pavement, Dodd and Hart would turn back everyone who wanted through, spinning a tale of a tanker-truck accident.
        Clockwork.
        When Jack and Pollard got to the rear of the truck, Chad Zepp was already there. In the glow of a battery-powered light that he had fixed to the truck with a magnet, Zepp was unscrewing the faceplate that covered the lock mechanism on the doors to the cargo hold.
        They had brought explosives, but when trying to peel a truck as well-constructed as the Guardmaster, there was a risk that explosives would fuse the lock pins, sealing the honeypot even tighter. They had to try going in through the lock, leaving explosives as a last resort.
        Some older armored cars had locks that operated with a key or pair of keys, and some had combination dials, but this was a new vehicle with state-of-the-art equipment. This lock was engaged and disengaged by pressing a sequence of code numbers on a ten-digit keyboard that was the size and appearance of the "dial" on a touch-tone telephone. To activate the lock, the guard closed the doors and simply punched in the middle number of the three-number code. To deactivate it, he pressed all three numbers in the correct order. The code was changed every morning, and of the two men crewing the truck, only the driver knew it.
        There were one thousand possible three-number sequences in ten digits. Because it would take between four and five seconds to key in each sequence and wait for it to be accepted or rejected, they would have to delay at least an hour and a quarter to try every combination. That was far too risky.
        Chad Zepp removed the faceplate from the lock. The ten numbered buttons remained, but now it was possible to see a bit of the mechanism between and behind them.
        Hung on a strap from Zepp's shoulder was a battery-powered, attaché-sized computer, which could assess and control the circuitry of electronic locks and alarms. It was SLICKS, an acronym for Security Lock Intervention and Circumvention Knowledge System. Intended solely for military or intelligence-agency personnel with security clearance, SLICKS was unavailable to the public. Unauthorized possession was a criminal violation of the Defense Security Act. To obtain a SLICKS, Jack had gone to Mexico City and had paid twenty-five thousand dollars to a black-market arms dealer who had a contact inside the firm that manufactured the device.
        Zepp unslung the computer and