He left the boy outside its own front door. Farewell to it, and good luck to it. From here on in it would be squared shoulders and jaws, and strong arms and best feet forward. He left the boy a pile of mangled, skinny limbs and stepped through the door a newborn man, stinging a little in the sights of the sprite guiding his metamorphosis. Karine D'Arcy was her name.
-- Narrator (chapter 1 paragraph 1)

Importance: This quote opens the novel and highlights the importance of growth and social relationships that will continue throughout the novel. This quote specifically speaks to the conditions of Ryan's manhood; Ryan has left behind the "mangled" ruin of a boy and stepped into a manhood dependent on Karine D'Arcy. The passage also emphasizes the importance of the threshold of the Cusack home: where Ryan leaves his boyhood, where Georgie is turned away when asking about Robbie, and where Tony watches...