上星期我朋友的公司出现了一起风波。一名会计被发现挪用公款。他连续几个月没被发现，因为他做得很隐蔽。我们可以用一个习惯用语来形容他的这种做法。那就是：cover one's tracks。
Cover意思是“隐瞒，掩饰”，tracks是“轨迹”。连起来to cover one's tracks的意思就是“掩盖行踪，隐瞒证据”。
- The accountant was able to cover his tracks for a long time before his scheme was finally discovered.
这位会计长期隐瞒证据，直到他的阴谋被发现。
下面的例子里，一名罪犯越狱之后是如何掩饰自己行踪的呢？我们赶快来听听看：
- The prisoner escaped weeks ago. The police had a hard time finding her because she covered her tracks. She was careful not to use her real name and she kept traveling from one state to another. When her photo appeared on TV, a viewer reported seeing her. And she was finally captured.
这名犯人几星期前越狱，警方费了好大力气搜捕她，但是她很好地掩盖了自己的行踪。她不使用真名，而且不停在州与州之间转移。直到她的照片被公布在电视上，有人举报说曾经见过她，才终于把她抓了回来。
现在高智商犯罪真是越来越普遍！很多犯罪分子不但聪明，还会利用高科技手段来掩盖自己的所作所为。我还记得前几年大热的美剧：Prison Break《越狱》，里面的男主角Michael就是这样：
- He was able to cover his tracks with a complicated underground maze.
他挖了一条复杂的地下迷宫来掩饰行踪。
大家都喜欢惊喜派对。下面的这个例子里，兄妹俩人为了给他们的妈妈制造一个惊喜派对，一直试图掩饰他们的计划。让我们来听听看他们都做了些什么：
- Mom and dad have no idea that we're organizing a party to celebrate their 50th wedding anniversary. So far we've been pretty good at covering our tracks. If we let them think that we and the other guests have other plans that weekend, they won't find out what's really happening. Then it'll be a big surprise!
妈妈和爸爸完全不知道我们为他们50周年结婚纪念日准备了一场派对。到目前为止，我们的掩饰工作做得还不错。如果我们能让他们以为大家在那个周末都有别的安排，他们就完全不会知道我们真正的计划。那就真是个大惊喜了！
所以说，cover one's tracks也不一定都是干坏事。我同事有一次也给了我这样一个惊喜。他们计划了一次特别的午餐会庆祝我晋升，但是却骗我说这是一次编辑会。
- They carefully covered their tracks so I didn't find out about the surprise lunch party!
他们小心掩饰，所以我一点也没发现，原来那是一次惊喜午餐会！
