how does the outcome of billys surgery affect reuven

Potok returns to the events of the hospital when Reuven calls Billy and learns that his surgery was unsuccessful; this reminds the reader of how far the story (and, by extension, the characters) have progressed in the past chapters. Also, by noting that Reuven does not see Danny for nearly a week suggests that the two are now quite close, for the fact that they do not see each other is a described as a change of events.