They've no let grass grow under their feet in hunting out the man that did it. 误译：他们没有让脚下长草就追捕了做这件事的人。 正确：他们说干就干，很快就把凶手抓到了。 说明：not let grass grow under one's feet 的意思是“说干就干；毫不迟疑；不浪费时间；不错过机会”。