元朝有位杂剧作家康进之，
曾编过《李逵负荆》这出戏。
演的是北宋末年天下乱，
农民们纷纷闹起义。
就在山东梁山泊，
有许多英雄好汉来聚义，
为首的大名鼎鼎叫宋江，
正筹划进一步扩大根据地。
靠水泊有一个村子叫杏花庄，
庄头上开一个酒店悬酒旗。
开店的老板叫王林，
年纪也有六十几。
有一个女儿名叫满堂娇，
父女俩相依为命过日子。
有一天两个流氓进店来，
耍无赖就把老汉女儿欺。
这俩贼自称都是水泊人，
假冒鲁智深宋江俩人名。
老王林女儿遭灾心悲痛，
正哭时李逵下山到这里。
老王林一番哭诉激英雄，
黑好汉信以为真生怒气，
似旋风回到梁山寨，
忠义堂前拿板斧劈，
一斧砍倒杏黄旗，
逼宋江去和王林亲对质。
到后来事情真相弄大白，
方知道，罪犯是流氓和地痞。
错怪了哥哥非小可，
最不该一怒砍倒聚义旗。
好李逵脱去上衣负荆条，
找宋江认错又赔礼。
宋江说，真正坏人未捉到，
光是赔礼有啥用！
恰巧是王林上山来报告，
说坏蛋又到他店里。
他女儿也被带了来，
俩坏蛋已被灌醉在梦里。
宋江叫李逵快去捉坏蛋，
李逵说，瓮中捉鳖很容易。
飞快去抓来坏蛋正了法，
李逵也深深受教育。
“瓮中捉鳖”作成语，
常比喻坏人早已被控制，
逃跑已是不可能，
若要捉住很容易。
Catch a Turtle in a Jar
In the Yuan Dynasty（1271—1368A。D。）there was a playwright by the name of Kang Jinzhi。He composed a play titled“Li Kui Apologizes”。It tells the story of the warring Northern Song Dynasty。The peasants had an uprising now and again。It was by the water margin of Liangshan in Shandong Province。Many a hero gathered together。The commander is the famous hero named Song Jiang，who was planning to enlarge his base。Beside the water margin there was a village named“Almond Blossom Village”。In front of the village there opened a restaurant。The proprietor of the restaurant was Wang Lin。He was already in his sixties。He begot a daughter named Man Tangjiao（meaning dear in the whole house）。Father and daughter lived a well-to-do life。
One day two hooligans came into the restaurant，and shamelessly took the girl away。They called themselves Lu Zhishen and Song Jiang，two masters from the troop on the water margin。Old Wang Lin was crying over the disaster when Li Kui got there having come down from the mountain of the water margin。Old Wang's sad story stirred up the hero。This black guy assumed it true and got furious，and in quite a whirl he went back to the quarters，raising his ax in front of the“Loyalty and Humane Hall”。He felled the apricot-yellow flag，and forced Song Jiang to confront Wang Lin。
Later they knew what the truth was。The criminals were two scoundrels。It was terrible to wrong my dear brothers，and it was even more terrible to fell the flag。The smart man bare-backed proffered a birch，and asked Song Jiang for a flogging。Song Jiang said that now that they had not caught the bad guys，what was the meaning of the apology。Just then Wang Lin came to report，that the two scoundrels haunted his restaurant again。His daughter had been brought here，and the scoundrels had been made drunk to sleep。Song Jiang asked Li Kui to catch the bad guys。Li said it would be just like catching a turtle in a jar。He promptly went there and crushed the robbers to death，and drew from it quite a good lesson。
“Catch a Turtle in a Jar”as an idiom indicates the bad men have already been under control。As it is impossible to flee，you can easily take hold of them。
