Cao Cao’s water borne troops of twenty thousand men are all wiped out. Zhou Yu holds a victory banquet for Gan Ning. At night, Zhou Yu observes Cao Cao’s naval camp. On returning to his own troops, he hears Lu Su saying that the commanders-in-chief of Cao Cao’s water borne troops are Cai Mao and Zhang Yun. Zhou Yu wants to kill Cai Mao and Zhang Yun. In order to do that he needs a stratagem to sow discord among the enemy. Cao Cao sends Jiang Gan across the Yangzi River to try to ascertain the military strength of Zhou Yu. Jiang Gan becomes confident that he could persuade Zhou Yu into surrendering. When Zhou Yu receives news that Jiang Gan has arrived he sets his plan into action. He fools Jiang Gan into deceiving Cao Cao.
曹操水師兩萬人全軍覆沒。周瑜爲甘甯擺慶功酒。夜間，周瑜看曹操的水寨，然後回軍中，他聽魯肅說曹操水師正印都督是蔡瑁、張允，周瑜想欲殺蔡、張，必須用反間計。曹操用蔣幹過江，探聽周瑜虛實，蔣幹認爲可下說辭勸周瑜投降，周瑜得知蔣幹前來即用反間計，欺蔣幹轉欺曹操。