This dialogue is worth learning because there are many language points in it . Now let's have close look at it .
A : I didn't expect to see you at this hour , you must have goofed off.
B: Goofed off? Maybe , but I'm not a clock- watcher. I finished doing what I should do and then knock off an hour earlier .
A : You'll be sorry if the boss finds it out. He maybe gives you the bag.
B: I am sure of what I am doing .

【對話講解】

1 I didn't expect to see you at this hour.
我不希望在這一點看見你。

這句我們聯系上下文，是A委婉的告訴B所犯的錯誤，就是還不到上班點就看到B離開了。因此他想說我希望不是在這時看到你，而應該是在下班的點數才看到你。In another word , this means "I expect to see you at the closing time.'

2 you must have goofed off.
你一定是又在混日子了。
這句用的是情態動詞的虛擬語氣，注意這個結構 must have done 是對過去發生的事情的非常肯定推測。

3 Maybe , but I'm not a clock- watcher.
也許吧，但是我不是一個看重點等著下班的人呢。
這里maybe 插入中間，是一種無奈的語氣。

4 I finished doing what I should do and then knock off an hour earlier .
這里what I should do 是賓語從句。Finish 后面要用動名詞形式。 An hour earlier 意思是提前了一小時，也可說ahead of an hour .

5 : You'll be sorry if the boss finds it out.

如果被老板發現你會后悔的。Sorry 在這里是后悔的意思。

6 I am sure of what I am doing .

我清楚我在做什么。
Be sure 是清楚地意思，be sure of sth. 是清楚某事，of 后面跟了一個賓語從句： what I am doing .

Well , so much for the explanations to the valuable dialogue . If we want to absorb knowledge, we need to do some exercises.

來源:可可英語 http://www.ccdyzl.cn/Article/201103/128221.shtml