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.
我们必须弄清这件事的内情 。
She got suspicious and decided to get to the bottom of it.
她起了疑惑,便决定弄个水落石出 。
2.She, too, is getting down to brass tacks.
get down to brass tacks 讨论实质问题;转入正题
Never mind the side issues, let's get down to brass tacks and thrash out a basic agreement.
别管枝节问题,让我们讨论问题的实质,以求得基本一致 。
Let's get down to brass tacks.
让我们言归正传吧 。