Their first Cambridge apartment, where they lived for the six months before he was drafted, was not on any top story but in the basement of a brick apartment building on Concord Avenue, with an eye-level view of a shady patch of pachysandra and myrtle, barberry and cotoneaster. The overplanted patch, hidden from the street, was a trysting place for cats, a feline bedroom and bathroom both. That summer and into the lingering warmth of fall the young Mackenzies had to leave, in lieu of air-conditioning, their screenless windows open; more than once Owen awoke with a jowly yellow tom, whom they had nicknamed Uncle Ugly Cat, sitting purring on his chest, his blue lips so close to Owen’s face the smell of rancid fish oil was nauseating. Phyllis, indecisive and fretful for the first time since he had known her, drifted through her course in probability (combinational analysis, random variables, laws of large numbers, recurrent events, Markov chains, prediction theory) and still groped after a Ph.D. thesis topic, unable to find, in the vast tangle of achieved mathematics, an unformulated scrap she could make her own, while Owen, an ill-paid apprentice at the Harvard Computation Laboratory, struggled, in this twilight of the ponderous Mark I, with the primitive programming system called the A–O compiler and with the complications of hard-disk data storage, an innovation that would liberate the machines from programs on cumbersome punched cards or reels of magnetic tape. Already IBM had marketed, to government and research departments, the first commercial computer, the 701. The visions that these developments opened up, of ever more intricate workings down in the tiny layered circuits, an abstract processing not only exponentially faster and smoother than human thought but single-track, a spark hurtling round and round the algorithmic loops until it arrived at the programmed decimal margin that determined practical equivalence—a clean, lightning-fast process the opposite of many-branched human thinking, that mist of incalculable factors, emotional, egotistical, and sensual.