Now Janson stood atop the balustrade and leaped the short distance to the adjoining house. He had an objective. The AKS-74: a crude, chattering, powerful submachine gun. He landed imperfectly, and pain shot like a bolt of electricity up his left ankle. A bullet twanged through the air just inches from his head, and he threw himself down on the tiled peak, a few feet away from the man he had just shot dead. The too-familiar smell of blood wafted toward him. He reached out and wrested the submachine gun from its nylon sling, hastily cutting it free with a pocketknife. Without shifting his position, he craned his head around to situate himself.

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.