"You never can tell," Nick said wisely.  His mild eye, travelling round, encountered Tom’s, and, struck by something in his child-like expression, examined him yet further.  The end of an ivory crutch-handle, tucked tightly under Tom’s arm, caught and held his glance, and for a moment he looked unutterable things.  Then he bestowed his attention anew upon Pa Smith, moving a little so as to interpose his person between him and Tom. He felt a grateful dig as Tom slipped past him.