Chess Tactic of Destiny!

To win an important chess event like the Candidates, sometimes you need a little luck!

Here is the position that changed the entire outcome of the Berlin Candidates Tournament. If Kramnik found the right continuation, he would have been +3 and we may have seen a completely different winner. However, Kramnik missed it and Caruana capitalized on it and won the game. He never looked back.

White to move. How should white proceed?

Kramnik v Caruana (round 4 of Berlin Candidates)