Tricky Astonishing Puzzle!

Black to play!
Try solving it yourself, using an engine won't help you improve.

Is it 1...Qxb4 2.cxb4 Rc1+ 3.Kxc1 bxa2 and black promotes, a queen up for the rook??
There's probably something deeper going on but it's late and I only gave it a quick look.

Is there a checkmate? I see a winning position with a trade and a check.