Communications in the past - 50 years ago, two men made a pact to duel 50 years later. But without proper means of contact, how will they find each other? 五十年后要在这棵树下再比高下，到底怎么约啊？在没有手机电邮面簿的年代就只讲求信用。丢了手机能再买一个，但丢了信用——哪里找啊？