When they arrived Wednesday evening at the Aquatics Centre, the four young women — Missy Franklin, Dana Vollmer, Shannon Vreeland and Allison Schmitt — clasped hands, a symbol of solidarity for what would happen in the hours to come. When Vreeland touched the wall in the pool and Schmitt dove in for the final leg of the women’s 4x200-meter relay at the London Olympics, there was surely doubt among the thousands of fans, some of whom screamed for the Australians, who held what looked to be a commanding lead.

But beyond the perceived stars of this American team — past Ryan Lochte and Michael Phelps, past even teen sensation Franklin — there is both depth and desire, plenty of places to turn for hope. When Schmitt hit the water, she was more than a half-second behind Australia.

“There was no doubt,” said Bob Bowman, Schmitt’s coach.

“I knew Allison was going to pull off something amazing,” Vollmer said.

So Schmitt did, lifting the American women to their first gold medal relay performance in eight years with a blistering leg that was nearly one-and-a-half seconds faster than any other woman on any other leg of any other team. This, to finish off a night in which decidedly out-of-the-spotlight Nathan Adrian stunned favored James Magnussen of Australia in the 100-meter freestyle — an outcome determined by a fraction of a finger’s snap, all of one one-hundredth of a second.

Throw in a world record by 200-meter breaststroker Rebecca Soni — a performance that came in a semifinal, but makes her the heavy favorite to lower that number in Thursday’s final — and Phelps and Lochte could step aside, swim some heats and cheer on what has become a loose, confident American team.

“We’re just starting to pick up more and more steam,” said Phelps, who swam only the preliminaries and semifinals of the 200-meter individual medley Wednesday. “Hopefully we can finish this.”

Wednesday was a large step toward that, and its stars weren’t those who dealt with unbearable buildup over the past few months. Adrian, 23, is known only to the swimming community — a winner on relays, but never with an individual medal at world championships or the Olympics. In the 100 freestyle, his opponents included Cesar Cielo, the world record holder from Brazil; Yannick Agnel, the hero of the victorious French 4x100 relay team; and Magnussen, who brashly arrived at the Olympics as part of an Australian men’s team that dubbed itself the “Weapons of Mass Destruction.”

So Adrian simply had to take himself to a different place. It’s not the Olympics.

“That’s the best place for me, being that fourth-grader on the playground kind of oblivious to it all,” Adrian said. “That’s where I’m comfortable.”

He’s also comfortable racing this tactical event from a deficit. He stood third at the midway point, and he was soon up against Magnussen, who swam with a reputation as a sterling closer. Adrian, overlooked all week, could have been forgotten again.

“That’s not motivation,” Adrian said. “It’s kind of comforting, to be honest. I like being a chaser. I don’t necessarily like being the one being chased.”

So he chased. Magnussen had a narrow lead with 25, then 15, then 10 meters to go. In the ready room, where they waited to swim their 200 IM semifinals, Phelps and Lochte watched the race together.

“We were both cheering and cheering and cheering,” Phelps said. “And as soon as he won, Ryan and I went nuts.”

Adrian, though, didn’t know right away that his hand — outstretched fingers attached to an outstretched wrist at the end of an outstretched arm — had touched almost imperceptibly first. When he finally blinked away the drops from his eyes and saw the scoreboard — Adrian, 47.52 seconds; Magnussen, 47.53 — he slapped at the water and let out a wail.

“It was a moment of disbelief,” he said.

The women, in turn, had quite a believable moment in what’s becoming an unbelievable week. The plan was simple: Give Schmitt a position in which she could at least see the leaders, and she would reel them in over the final 200 meters. She already had won the gold medal at that distance earlier in the week, and with four medals in four swims, two of them gold, she is on a short list of potential swimmers of the meet.

“She’s really learned the mental game,” said Bowman, who also coaches Phelps. “. . . She’s focused when she needs to be focused. She’s relaxed when she needs to be relaxed. She knows how to use her energy.”

She used it all on that last leg. Australia handed a lead of .54 seconds to Alicia Coutts, its anchor. She stood no chance. After the midway point, when the American team trailed by .63 of a second, Schmitt crushed Coutts. When she touched the wall for the final 50 meters, she had completely flipped it — taking the lead by .63 of a second. Her teammates stood on the pool deck, huddled and waiting.

“I just wanted to bring it home for them,” Schmitt said.

She did, giving the Americans an Olympic record 7 minutes 42.92 seconds — 1.49 seconds faster than Australia, a yawning 4.57 seconds faster than third-place France. The embrace when Schmitt climbed from the pool was all-encompassing and heartfelt, because winning a relay after so much time “means the world to us,” Franklin said.

On the medal stand, the four women clasped hands once again. They laughed. They sang the national anthem. Then they walked around the pool, waving and wrapping themselves in a flag. And then they held hands again, the final sign of togetherness for an American team that has three more days to show how together they are.