【关键句讲解】
There are two sentences in this dialogue, being worth polishing them.
1 I heard Beth's surprise birthday party is on Sunday.
【翻译】我听说Beth的令人惊喜的生日晚会定于周日进行。
【要点】surprise 这里是名词作定语，可以改为surprising.

2 I don't want her to find out.
【翻译】我不想让他知道。
【要点】to find out 是动词不定式做宾语her的补足语。In this sentence, it means "know".意思是知道。 For example: We must find out the customs of other countries, so that they will not think us ill mannered. 我们必须知道别的国家的习俗，免得他们会认为我们是没有礼貌的。Another sentences is :Find out what the conditions of the contract are. 弄清楚合同的条件是什么。Here it means "make something certain". 意思是：弄清楚。We have another sentence: I shall make it my business to find out who is responsible. 我要查出是谁的责任. In this sentence , it means "get the answer by examination". 意思是：查明，找出。If the boss should find out about this, heads will roll. 万一被老板发现，饭碗可就保不住了。在这句话中，意思是：发现。