In the second act of the play the plot thickens .

剧情在第二场开始变得复杂起来。

As the cloud thickens , some pilots are asking .

由于云变厚，有些飞行员询问.

Epo thickens the blood , and it also has proved dangerous .

epo虽然使血液变稠，但它也被证明是危险的。

Now the plot thickens again .

现在情节又复杂了。

And what that does is it thickens this iayer of atmosphere .

问题是大气层变厚了之后。