What does it mean when Roger felt the "taboo of the old life"? Also, what does it mean when Jack approached Roger "a darker shadow crept beneath... [Roger's] skin."? What effect is Jack having on Roger?
It means that when Roger was doing mean things to the littluns, there was a psychological effect on him; it caused him to remember the repurcussions that cruelty would've involved in his old society. At this point, Roger still feels limited by authoritative figures like adults, policemen, school rules, and laws even though he could technically do whatever he wanted to. Also, when Roger recalls being around Jack, he says a dark shadow crept beneath his skin. I think that means that Jack brings around a sense of evilness and that influences the way that Roger treats other people.