Drew Storen was handed a 7-5 lead in the ninth inning, but the Nationals' 25-year-old closer allowed four runs to give the Cardinals a 9-7 lead heading to the bottom of the ninth.
Storen allowed a double to Carlos Beltran leading off the ninth, then retired the next two Cardinals hitters and got two strikes on Yadier Molina to bring the Nationals to within a strike of the National League Championship Series.
He then walked Molina and David Freese, loading the bases for Daniel Descalso.
Descalso ripped a two-run single off the glove of shortstop Ian Desmond, bringing in two runs to tie the game. Pete Kozma then followed with a two-run single to right, and in the blink of an eye, the Nationals trailed by two.
They had led 6-0 after three innings.
They had led 7-5 entering the ninth.
Now they trail 9-7 and are three outs away from elimination in a shocking turn of events which has stunned the largest crowd in Nats Park history.
Update: That's it. Just like that, the Nationals' dream season has come to an end.
Jayson Werth, Bryce Harper and Ryan Zimmerman went down in order in the bottom of the ninth, and the Cardinals spilled out of the dugout to celebrate their 9-7 victory and berth in the NLCS.
This one will sting for a long, long time. The Nats were oh, so close to moving on, and now they go home.