或說天下未有兵甲時，常多刺客。

It is said that when a society is in tumult, assassins are not uncommon.  

李汧公勉為開封尉，鞫獄，獄囚有意氣者，感勉求生，勉縱而逸之。後數歲，勉罷秩，客游河北，偶見故囚。故囚喜迎歸，厚待之，告其妻。曰：“此活我者，何以報德？”妻曰：“償縑千匹可乎？”曰：“未也。”妻曰：“二千匹可乎？”亦曰：“未也。”妻曰：“若此，不如殺之。”故囚心動。 

When Sir Li Man was the chief sheriff of Kaifeng County, once he conducted an interrogation and trial.  One of the suspects seemed composed and asked Li to set him free.  Li was moved and then released him.  Several years elapsed, Li left office and went to Hebei.  Accidentally, he run across that suspect there.  The suspect was happy to see Li again and took him to his house, entertaining him with generous treat.  He also told his wife that Sir Li had saved his life and asked her how to repay Li.  His wife replied to him that if a thousand Pi of silk is enough.  He said, "Not enough".  "How about two thousand Pi of silk?"  "Not enough, either."  Then his wife said, "If so, we had better kill him."  That suspect was persuaded.

其僕哀勉，密告之。勉衩衣乘馬而逸。比夜半，行百餘里，至津店。店老父曰：“此多猛獸，何敢夜行？”勉因話言。言未畢，樑上有人瞥下，曰：“我幾誤殺長者！”乃去。未明，攜故囚夫妻二首，以示勉。

A servant of the house sympatized Li and told him that evil scheme.  Li, even yet to properly dress, rode away at once.  After having ridden over half a hundred miles, Li arrived at an inn near a ferry.  The innkeeper wondered how did Li dare riding alone in the night along the road that is haunted with beasts.  Li told him the reason why.  No sooner had Li finished his story than an assassin jumped down from the beam and said, "I almost killed a noble and righteous man.", then disappeared. 

Before daybreak the very next morning, the assassin brought the heads of that suspect and his wife to Li.