The Nats were up 3-2 in the bottom of the 12th inning, when the Astros' Brett Wallace came to the plate with runners on first and second. Wallace gave a Tyler Clippard offering a ride to deep left-center field, and Bernadina made a leaping catch into the wall to end the game in incredible fashion.
Here's video of the catch:
And aside from it just being an awesome play, it could look very big down the road, as the Nats currently hold a four-game lead on the Atlanta Braves in the National League East. If the Nats win the division by one game (or go to that stupid new play-in format and get in playoffs that way), this catch will look huge.