When the Map is Unrolled，the Dagger¹ is Revealed

图穷匕现

In the end of the Warring States Period，there was a strong country named Qin. It wanted to annex² other countries to unite China. In 228 BC，the Qin army captured a country and prepared to attack another country named Yan. So the prince Dan of Yan sent a brave man called Jing Ke to assassi-note the King of Qin.

战国末期，有一个很强大的国家叫秦国，它想吞并其他国家，统一天下。公元前228年，秦国的军队占领了其中一个国家。接着又准备人侵另一个叫燕国的国家。燕国的太子丹就派了一名叫荆柯的勇士前往秦国刺杀秦王。

In order to gain the confidence of the King of Qin，he carried a map of the most fertile part of Yan territory to Qin and hid a sharp dagger in it.He came to Qin and entered the palace.When the king ordered the map be presented，he took out the map and presented it to the king with great re-sped. Slowly，he unrolled the map.When it was completely unrolled，the hidden dagger appeared. Jing Ke grabbed it and stabbed at the king. But the king dodged³ the dagger and hid himself behind a big pillar. Jing Ke had never got the chance to kill the king as he was soon killed by the palace guards. The plan has failed. Later，Qin had wiped off Yan.

为了获得秦王的信任，荆柯带上了一张地图，上面画着燕国最富饶的地方，准备献给秦王。他在这张地图里藏了一把非常锋利的匕首。他来到秦国，见到秦王，恭敬地将地图献_L，然后，慢慢打开地图给秦王看。当地图完全打开时，他抽出那把藏着的匕首，刺向秦王〔。但秦王躲开了，跑到了一根大柱子后面。秦王的卫士们立刻跑来围住他，马上就把他杀了。燕国太子刺杀秦王的计划失败了。后来，燕国也被秦国给吞并了。

The idiom describes the real intention is revealed in the end.

后来，人们用这个成语来比喻事情发展到最后，真相或本意就露出来了。