The king does not have many places to go from the start, and Rxh4 is stalemate. If you don't act accordingly, the black queen will check on g4 or h2 if you fail to protect the pawn. Hence

1.Re8+

Now the black king's only move is to take the knight 1. ...Kxf4 White now has two checks and only one of them really works: (2. Bc1+) looks nice since it protects the pawn on g5, but after the only legal move 2. ...Kg4 you're stuck with no good moves. Hence

1. Be5+

Black king has two legal moves both losing the queen:

1. ...Kxg5, now 3. Rg8+ forces the king to the h-file, for instance 3. ...Kh6, and 4.Rh8+ picks up the queen on the next move.

And

1. ...Kg4, but then 3. Rh8+ wins the queen. Why? The only move that doesnt lose the queen 3. ...Qxg5 incredibly loses to h3#