Seventeen miles into the 1936 Boston Marathon , he led by a half mile. Wearing white shorts and a white singlet , with a boxer’s biceps and pecs, the stranger carried the aura of a Greek god as he made his way up the first of the four Newton Hills. His stride was smooth and loping and his concentration total, so that as he ran he seemed never to look left or right. His dark brown eyes simply fixed on the horizon. The crowd favorite was the marathon’s defending champ, Johnny Kelley. A diminutive 28-year-old gardener from nearby West Medford, Massachusetts, Kelley was an Irish Catholic hero in a city teeming with Irish Americans. A typical news account of the era described him as a “smiling Irishman.” And when he reached the Newton Hills, he began to close on the stranger, ferociously, undertaking what was later called “one of the most furious runs through the hills in history.” Lining the course, watching, were hundreds of thousands of spectators bundled in long coats against the April chill.…