U.S. wrestler Helen Maroulis competes on Aug. 18 in the 53kg division of freestyle wrestling. (Jonathan Newton/The Washington Post)

Helen Maroulis wandered through London streets four years ago, fighting depression in the place she expected to live her dream. She planned to compete at the Olympics, and she would have if not for one mistake, one takedown during the final match at the U.S. trials. So instead she had come to practice, to be used as a prop for the woman who took her place.

The essence of wrestling is cruelty, and four years ago, Maroulis faced one its cruelest customs: Coaches invite the second-place finisher to serve as a training partner for the Olympian. A few months after Kelsey Campbell beat her in the final, Maroulis traveled to London to help Campbell chase the precise goal she lost.

“Being that No. 2 person, you’re totally crushed,” U.S. women’s wrestling Coach Terry Steiner said. “Your dreams are crushed. Then you’re being asked to go help someone who just beat you. You really have to swallow your pride.”

Maroulis, a Rockville native who attended Magruder High, wanted to hide. In London, though, the spirit of the Games lifted her, and in a bitter moment she derived inspiration. She resolved she would return to the Olympics but as a participant.

“There’s no way I’m going to let this opportunity get past me again,” she told herself.

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Maroulis is in Rio de Janeiro now, a reigning world champion and harboring realistic hopes of a gold medal in the 53-kg weight class. She dominated April’s trials in Iowa and then held back tears. Her path had started four years ago in the same arena.

Entering the 2012 U.S. trials, Maroulis had not lost in 18 months. Campbell took her down for the only points of the championship. Months later, Steiner asked her to come to London.

“I didn’t want to,” Maroulis said. “I was heartbroken. But it’s a great sport. It’s going to teach you through the adversity. So I went.”

The role required total submission. Maroulis had been ranked No. 1 in the United States and used to receiving constant attention from coaches. Now she had to serve Campbell. It didn’t matter how sore she felt or what nagging injuries she suffered.

“You’ve got to come do what she says,” said Maroulis, a Rockville, Md., native who attended Magruder. “If she wants to drill on you all day, you’re in the room for hours, but you don’t take a single shot, well, that’s what you got to do.”

One day in London, Steiner took Maroulis aside. “This isn’t your time right now,” he said, “but your time is coming.” He told Maroulis she would be the best in the country again, but if she folded as a training partner, her teammates would remember it always. They would never see her as a champion but only as somebody unwilling to sacrifice. Campbell lost both matches in London, to the eventual gold and bronze winners. But Maroulis threw herself into her job.

“What I’ve found is, it’s so healing for them, too,” Steiner said. “You can’t be bitter for the rest of your life. We knew that she wasn’t done. We knew she had a future. But if even you were done, you can’t hold on to that forever. The best way to pull through hard times like that is help someone, help them achieve something.”

The first step in the path to Rio, then, occurred on those harsh mornings in London. Having made it, she found a new appreciation for the 2012 Games.

“It would be really hard to enjoy this position that I’m in if I knew that as a training partner, I wasn’t a good partner, I wasn’t a good friend, I wasn’t good teammate,” Maroulis said. “It wouldn’t sit well with me right now. At the time, I wanted to fight against it, just being honest. But it really taught me I’ll be proud of myself, no matter what, based on the way I carry myself.”

In the past four years, Maroulis emerged as one of the best in the world. She won the world championship in 2015 after moving down a weight class and a brutal fight to make weight. Before the trials, she felt nerves gnawing at her. She remembered what she was told in London, and she decided she would not let herself miss another opportunity.

“Now,” Steiner said, “I think she’s really ready to go do it.”