最后一句thecurtainisabouttobedrawnaside什么意思？
After the college-board examinations in June, Basil Duke Lee and five other boys from St. Regis School boarded the train for the West. Two got out at Pittsburgh, one slanted south toward St. Louis and two stayed in Chicago; from then on Basil was alone. It was the first time in his life that he had ever felt the need of tranquility, but now he took long breaths of it; for, though things had gone better toward the end, he had had a / an unhappy year at school.
He wore one of those extremely flat derbies (常礼帽) in vogue during the twelfth year of the century, and a blue business suit became a little too short for his constantly lengthening body. Within he was by turns a disembodied (空洞的) spirit, almost unconscious of his person and moving in a mist of impressions and emotions, and a fiercely competitive individual trying desperately to control the rush of events that were the steps in his own evolution from child to man. He believed that everything was a matter of effort — the current principle of American education — and his fantastic ambition was continually leading him to expect too much. He wanted to be a great athlete, popular, brilliant and always happy. During this year at school, where he had been punished for his “freshness,” for fifteen years of thorough spoiling at home, he had grown uselessly introspective, and this interfered with that observation of others which is the beginning of wisdom. It was apparent that before he obtained much success in dealing with the world he would know that he’d been in a fight.
Fifteen is of all ages the most difficult to locate——— to put one’s fingers on and say, “That’s the way I was.” And all one can know is that somewhere between thirteen, boyhood’s majority, and seventeen, when one is a sort of counterfeit young man, there is a time when youth fluctuates hourly between one world and another —— pushed ceaselessly forward into unprecedented experiences and vainly trying to struggle back to the days when nothing had to be paid for. Fortunately none of our contemporaries remember much more than we do of how we behaved in those days; nevertheless the curtain is about to be drawn aside for an inspection of Basil’s madness that summer.
本段中Fifteen is of all ages the most difficult to locate怎么理解？ 最后一句the curtain is about to be drawn aside for an inspection of Basil’s madness that summer.什么意思？和上文有关系吗？最后一段大意讲什么？