When the Map Was Unrolled, the Dagger Was Revealed
Qin State was the most powerful among the seven states during the Warring States Period and never ceased to nibble the territories of the other six in order to unify. Qin troops marched north and besieged Handan, the capital of Zhao State, in 228 BC. Since the King of Zhao killed the famous general Li Mu wrongfully, at last the Qin troops occupied Handan, captured the King, and extinguished Zhao State.
The destruction of Zhao State put its north neighbor, Yan State, in imminent danger. To avoid the threat, Prince Dan of Yan State decided to send Jing Ke to Xianyang, the capital of Qin State, to assassinate Yingzheng, the King of Qin State.
Prince Dan made three careful preparations before Jing Ke, the assassinator's starting. First, he found a brave and strong man named Qin Wuyang to accompany him to Xianyang to help him. Moreover, he took with him the head of Fan Wuju, a betrayed Qin general, whom the King of Qin had been expecting to kill. Finally, he took the map of Dukang, the most fertile area of Yan, to present to Yingzheng. The last two arrangements would help Jing Ke win the trust of the king. The map had a special use, for rolled in it was a sharp dagger with its blade being soaked in virulent poison, which would be used to stab the king.
The King of Qin State was greatly pleased and began to open the map after he saw the head of his enemy and heard that Yan State would cede vast territories. As the map was unfolded, the dagger emerged. Jing Ke leapt up with a big stride, grabbed the dagger, and caught the king by his sleeve. Yingzheng struggled to escape with the sleeve torn up. Jing Ke pursued him around the big bronze columns for several rounds before the king obtained a chance to draw out his sword and hurt Jing Ke. Then the ministers and guards swarmed to kill Jing Ke with their weapons.
This idiom indicates that hidden intentions will be revealed in the end.
We should not harbor ill intentions against others, but never relax vigilance against evil-doers. Plots and tricks may not be disclosed until the last minute. In life we should be always honest with others.