Spoiler
47...b4 wins the queen. It has nowhere to run.
https://www.chess.com/analysis/game/live/111604362507?tab=analysis&move=91
It was a speed chess game that I watched live. White had plenty of time but he got impatient and missed it. I totally missed it too. The eval bar showed white with a huge advantage but I was mystified. I was looking in the wrong place - on the upper right side of the board. I forgot all about the b pawn. And they were playing so quickly I had brand-new other things to try to figure out.
The game was sharp. That's a chess term that I define as pretty damn complicated and tricky. Trying to understand the positions in real time made my head hurt.
No en passant would only work if blacks pawn is on A4.
Ah, I thought you could capture with en passant from either square. Goes to show that I haven't played chess in years
Obligatory: Google en passant.
Holy hell!