detection *
detecting
detective work
sleuthing

So you have to do some detective work to figure out what's really going on.

I'd done more than enough detective work for one day.

I'd like you to do a bit of detective work for me.

Then we went up to my office to do some serious detective work.

And a bit of good detective work on your part, too.

I'd just like to say in the first place that I think you did good detective work.

We'll have to do a little detective work on it.

"But first I'm going to take time out to do a little detective work."

Sometimes it's a matter of doing a little detective work.

All those months of detective work and he had nothing to show for it.