September baseball is a different sport than April-through-August baseball. Everything is magnified when a pennant is on the line. The fans are more gregarious. The players are more intense. And every play, heroic or horrific, can become a winter memory.

Tonight, St. Louis Cardinals pitcher Danny Cox made two mistakes, both in the first inning. He hit the New York Mets' George Foster, a man he wanted to pitch to, with a curve ball that didn't curve.

That was mistake No. 1. Mistake No. 2 was a fast ball three pitches later that third baseman Howard Johnson hit for a grand slam. That capped a five-run inning and gave the Mets just enough runs for a 5-4 victory that put them alone in first place, one game up on the Cardinals, in the National League East.

Ron Darling (15-5) pitched into the seventh inning before being rescued by 2 2/3 innings of superb relief pitching by rookie Roger McDowell. To the delight of many of the 50,195 at Shea Stadium, McDowell pitched out of a second-and-third, one-out jam in the seventh and a two-on, one-out jam in the eighth.

"When Rog came in for me, I was just hoping he would at least get (Willie) McGee out and keep us close," Darling said. "He did one hell of a job getting out of there with us still in the lead."

This was the first time since 1973 that the Mets entered a September series with even a share of first place, and Shea Stadium was full with eager fans, undaunted by the steamy weather or the threat of rain, before the first pitch.

"This is what you play for," said Mets first basemen Keith Hernandez. "This is what September is supposed to be all about."

It didn't begin well for the Mets, however. With two outs in the Cardinals' first, Darling grooved a 3-2 fast ball to Tommy Herr that ended up in the right field bullpen.

But the 1-0 lead was momentary. Mookie Wilson led off the bottom of the inning with a sharp single to center. After McGee made a fine backhand catch on Wally Backman's bloop to center, Hernandez came up. This was his first appearance at home since he admitted in court testimony Friday to use of cocaine while he was with St. Louis.

As Hernandez walked to the plate, the noise began to build, and by the time he stepped in, nearly all the fans were standing, giving him a lengthy, warm ovation. Clearly moved, Hernandez stepped out for a moment to calm himself.

Then he hit a 3-2 pitch to left-center. When Vince Coleman slipped on the wet turf going for the ball and booted it, Wilson, running on the pitch, had plenty of time to score, and it was 1-1.

Gary Carter grounded out and Hernandez moved to second. Cardinals Manager Whitey Herzog ordered Cox (15-9) to walk Darryl Strawberry in order to pitch to Foster.

"Anytime I can pitch to George Foster instead of Darryl Strawberry, I'll do it," Herzog said. "I put him on to pitch to Foster and then Cox hits him. Damn!"

The first pitch hit Foster in the left side. It appeared to be a pitch that just got away, but Foster chose to linger a few feet from the plate, glaring at Cox. When Cox walked off the mound, Foster, bat still in hand, said something. The two walked toward each other and the dugouts and bullpens emptied.

It turned out to be a waltz around the mound and no one threw a punch.

"I wasn't trying to hit him," Cox said. "Why would I do that? We wanted to pitch to Foster."

Up came Johnson, who sent a 2-1 fast ball well over the 371-foot mark in right center.

The rain came in the third, stopping play for 53 minutes. It cooled the temperature considerably and absolutely froze the Mets' bats -- they got two hits, both in the fourth, the rest of the night.

Darling gave up a run in the fifth, then ran out of gas in the seventh with a 5-2 lead. He started by walking weak-hitting Mike Jorgensen and Ozzie Smith. He got pinch hitter Steve Braun to ground into a force but immediately surrendered a double to Coleman. Jorgensen scored to make it 5-3, and Braun stopped at third.

Enter McDowell, the bubble gum-chewing rookie who has 13 saves this season.

"I was glad (Manager) Davey (Johnson) had confidence in me in that situation," he said. "I just wanted to throw my sinker and make them hit at somebody."

McGee did just that, hitting a ground ball at second baseman Backman, who threw him out as a run scored to make it 5-4. Up came Herr, Coleman now at third. Again, Herr hit the ball hard, but almost right at Strawberry in right.

There was one more scare in the eighth when Andy Van Slyke singled and Terry Pendleton reached on Carter's error. But McDowell got ground balls out of Jorgensen and Smith and a 1-2-3 ninth and they went into the now-cool night singing in New York.

"There are still 26 left," Hernandez said. "But we'll take it."