The planar geometry of the roofs was, he knew, deceptive. Peaks met peaks at what looked like perpendicular angles, but the angles were not truly perpendicular. Parapets that appeared parallel were not truly parallel. Eaves that appeared level were not truly level. Cornices and balustrades, built and rebuilt over the centuries, settled and shifted in ways that the quick glance would not detect. Janson knew that the human mind had a powerful tendency to abstract away such irregularities. It was a cognitive economy that was usually adaptive. And yet when it came to the trajectory of a bullet, small irregularities could make all the difference in the world. No angles were true; intuition had to be overridden, again and again, with the hard data of range finder and scope.

Now his hands patted down the dead man until he found and retrieved a small device with two angled mirrors attached to a telescoping rod that resembled the antenna of a transistor radio. It was standard equipment for an urban commando. Janson carefully adjusted the mirrors and pulled out the rod. By extending it over the cornice, he would be able to see what threats he still confronted without putting himself in the line of fire.

The weapon that was nestled in Janson’s arms was hardly a precision instrument—it was a fire hose, not a laser.

What he saw was far from encouraging. The deadly brunette was still in position, and though he was currently protected from her by the roofline geometry of the eaves, peaks, and gables, she would be alert to any movement, and he could not reposition himself without exposure.

A bullet thwacked into the chimney, chiseling off a piece of the centuries-old brick. Janson rotated the periscope-like device to see who was responsible. One roof over, standing with an M40 braced against his shoulder, was a former colleague of his from Consular Operations. He recognized the broad nose and quick eyes: an old-school specialist named Stephen Holmes.

Janson moved carefully, sheltering himself from the riflewoman by keeping himself low and behind the projecting brick gable while he snaked himself up the incline of the slate roof. He had to execute his next move perfectly, or he was dead. Now he kept his head down as his hands lifted the muzzle of the AKS-74 over the roofline. He relied on memory, on a fleeting image from the periscope, as he directed a burst of fire toward the long barrel of the rifle. An answering clang—the sound of metal-jacketed bullets striking a long barrel fashioned of a super-hard composite resin—told him he had succeeded.

Now he raised his head over the roofline and directed a second, more targeted burst: the steel-tipped bullets tore into the barrel of Holmes’s M40 until the green-black shaft shattered.

Holmes was now defenseless, and when his eyes met Janson’s it was with the resigned, almost weary look of someone convinced he was about to die.