His little bureau is dominated now by a glimmering map, a window into another landscape than winter Sussex, written names and spidering streets, an ink ghost of London, ruled off into 576 squares, a quarter square kilometer each. Rocket strikes are represented by red circles. The Poisson equation will tell, for a number of total hits arbitrarily chosen, how many squares will get none, how many one, two, three, and so on.

An Erlenmeyer flask bubbles on the ring. Blue light goes rattling, reknotting through the seedflow inside the glass. Ancient tatty textbooks and mathematical papers lie scattered about on desk and floor. Somewhere a snapshot of Jessica peeks from beneath Roger’s old Whittaker and Watson. The graying Pavlovian, on route with his tautened gait, thin as a needle, in the mornings to his lab, where dogs wait with cheeks laid open, winter-silver drops welling from each neat raw fistula to fill the wax cup or graduated tube, pauses by Mexico’s open door. The air beyond is blue from cigarettes smoked and as fag-ends later in the freezing black morning shifts resmoked, a stale and loathsome atmosphere. But he must go in, must face the habitual morning cup.

Both know how strange their liaison must look. If ever the Anti-pointsman existed, Roger Mexico is the man. Not so much, the doctor admits, for the psychical research. The young statistician is devoted to number and to method, not table-rapping or wishful thinking. But in the domain of zero to one, not-something to something, Pointsman can only possess the zero and the one. He cannot, like Mexico, survive anyplace in between. Like his master I. P. Pavlov before him, he imagines the cortex of the brain as a mosaic of tiny on/off elements. Some are always in bright excitation, others darkly inhibited. The contours, bright and dark, keep changing. But each point is allowed only the two states: waking or sleep. One or zero. “Summation,” “transition,” “irradiation,” “concentration,” “reciprocal induction”—all Pavlovian brain-mechanics—assumes the presence of these bi-stable points. But to Mexico belongs the domain between zero and one—the middle Pointsman has excluded from his persuasion—the probabilities. A chance of 0.37 that, by the time he stops his count, a given square on his map will have suffered only one hit, 0.17 that it will suffer two… .

“Can’t you… tell,” Pointsman offering Mexico one of his Kyprinos Orients, which he guards in secret fag fobs sewn inside all his lab coats, “from your map here, which places would be safest to go into, safest from attack?”

“No.”

“But surely—”

“Every square is just as likely to get hit again. The hits aren’t clustering. Mean density is constant.”

Nothing on the map to the contrary. Only a classical Poisson distribution, quietly neatly sifting among the squares exactly as it should… growing to its predicted shape… .

“But squares that have already had several hits, I mean—”

“I’m sorry. That’s the Monte Carlo Fallacy. No matter how many have fallen inside a particular square, the odds remain the same as they always were. Each hit is independent of all the others. Bombs are not dogs. No link. No memory. No conditioning.”