Nighty Knight, Walter Browne!

In this game, John Grefe faced off against Walter Browne in Moranwelz, 1973. Here, we see White's plan unfold with 14. fxg5? pinning it to his Queen. Later, White decided it was time to sacrifice his Queen for two minor pieces. Was this a fatal mistake for Grefe? Or, has eyeing that Queen poisoned Browne's position? It turns out that this dazling move by White was only to setup for 21. Nxd6+! in which Black resigns.