get to the bottom of something

I think we're getting to the bottom of something deep.

I love getting to the bottom of something while writing fiction - or trying to.

'I'm just trying to get to the bottom of something damned mysterious.

Mr President, surely it is necessary to get to the bottom of something like this.

If you want to get to the bottom of something, you don't appoint Henry Kissinger.

Of course they've regretted it afterwards, I've made sure of that but meanwhile I've been able to get to the bottom of something that's troubled them.

Followed by unrelenting questioning to get to the bottom of something a leader is believed to be hiding, pushing the leader to a point of anger, embarrassment or even humiliation to get a straight answer to a question he doesn't want to answer.