
White has just played 81.f6 and Keres resigned. Black is indeed losing, and even if the players weren't more than strong enough to figure out over the board why Black is lost, there had been two adjournments prior to this point. For us, however, it might not be immediately evident. It's a good exercise to work out how White wins this, especially against best defense by Black.
The solution, when you're ready for it, is here.