There's no 'mystery' (to/as to/about) why we're here. = It's no 'mystery' why we're here. [=we know why we are here]
His success is something of a 'mystery'. = His success is a bit of a 'mystery'.
We'll reveal the identity of today's 'mystery' guest after these commercials.
(..) that you all dress appropriately? Hmm. Four highly trained detectives and not one of you can solve this simple mystery. I wanna be briefed on any new developments. Any questions? I was gonna ask you if you thought I was doing (..)2013 TvShow: Brooklyn Nine-Nine Title: Pilot Season: 1 Episode 1