1.It means to get serious about something, to get to the bottom of the situation.
get to the bottom of 弄清真相
We must get to the bottom of the matter.
我們必須弄清這件事的內情 。
She got suspicious and decided to get to the bottom of it.
她起了疑惑,便決定弄個水落石出 。
2.She, too, is getting down to brass tacks.
get down to brass tacks 討論實質問題;轉入正題
Never mind the side issues, let's get down to brass tacks and thrash out a basic agreement.
別管枝節問題,讓我們討論問題的實質,以求得基本一致 。
Let's get down to brass tacks.
讓我們言歸正傳吧 。