HOUSTON - One moment, the whole ballpark was buzzing. The next, it was silent.

With one mighty swing, Albert Pujols saved St. Louis and stunned the Houston Astros.

"I've never heard 43,000 people shut up like that before," Cardinals outfielder Larry Walker said.

Pujols hit a prodigious three-run homer off Brad Lidge in the ninth inning and St. Louis rallied for a 5-4 victory Monday night in Game 5 of the NL championship series, denying Houston its first trip to the World Series.

Only one out away, the Astros were perched atop the dugout steps, ready to race onto the field for a wild celebration.

Only one problem - Pujols was at the plate.

"I just couldn't believe I did it," he said. "Couldn't be better than this."

Pujols' shot over the train tracks high above the left-field wall sent the series back to St. Louis for Game 6 Wednesday night, with Mark Mulder set to face Houston's Roy Oswalt. The Cardinals also staved off the wrecking ball at Busch Stadium, scheduled for demolition as soon as their season is over.

One strike from ecstasy before David Eckstein's ninth-inning single, the Astros dropped to an agonizing 0-5 with a chance to clinch the NLCS.

"It was devastating. We thought we were going to the World Series. We were there," Lance Berkman said. "Obviously, it was a high to a low, and it wasn't much fun."

After winning pitcher Jason Isringhausen closed it with two innings of scoreless relief, shocked fans filed quietly out of the ballpark.

They came to see something they had never seen before, their hometown heroes advancing to the World Series. Instead, they saw another kind of history.

It was only the second time in any postseason that a team facing elimination and trailing in the ninth inning hit a go-ahead home run, according to the Elias Sports Bureau. The other was Dave Henderson's homer for Boston off the Angels' Donnie Moore in Game 5 of the 1986 ALCS.

Berkman's three-run homer in the seventh off Chris Carpenter gave Houston a 4-2 lead, sending the crowd into a deafening roar, and the Astros appeared ready to wrap up this NLCS rematch.

They put their fate in Lidge's normally sure hands. But, trying for his fourth straight save in the series, he couldn't come through.

"This is a bump in the road, but there's no way this is going to get anybody down," Lidge said. "This will sting a lot tonight, but when I wake up tomorrow I'll be ready to go"

After Lidge struck out his first two batters in the ninth, the pesky Eckstein grounded a single to left on a 1-2 pitch. Jim Edmonds worked out a walk and Pujols, who had failed to deliver with runners on all night, drove an 0-1 pitch over the limestone facade.

Astros starter Andy Pettitte, in the dugout and ready to celebrate with his teammates, mouthed the words "Oh, my" as the ball left the park. Pujols tossed his bat and took a moment to watch the ball sail while Lidge sank into a crouch on the mound.

The Astros had been 84-1 this year when leading after eight innings, including the postseason.

"The guys coined the phrase, 'hard nine.' We're going to play a hard nine," Cardinals manager Tony La Russa said.

When Pujols got back to the dugout, La Russa grabbed him for a huge hug.

"He just told me, 'The Great Pujols,'" the slugger said. "They're going to be ready in St. Louis. We just need to win two before we lose one."

It was a crushing loss for the Astros and their "Killer B's." Craig Biggio and Jeff Bagwell are still trying to reach the World Series for the first time after 15 years as teammates.

"It's terrible. You're high as a kite one minute," manager Phil Garner said. "We were feeling pretty good, but you have to play every out."