it was the expression an explorer might wear when , after pushing his way through just one more nondescript tangle of bushes , he finds himself looking at some fabulous lost city or brain-busting geological feature-a cliff of diamonds , perhaps , or a spiral waterfall , ralph shrank back against the blue mailbox standing to one side of the drugstore 's entrance , still not breathing , his eyes shuttling jerkily from left to right as the brain behind them tried to understand the wonderful and terrible news it was receiving .