Missing in Milwaukee: A Mother's Quest for Justice

MILWAUKEE, Wis., Jan. 7, 2009— -- Karren Kraemer's daughter Becky Marzo vanished from Milwaukee, Wis., more than five years ago and since then Kraemer has fought a relentless campaign against the man she suspects is responsible for her daughter's disappearance: Marzo's boyfriend Carl Rodgers.

Watch the story tonight, January 7th, on a special hour of "20/20" at 9 p.m. ET

"It was about letting him know that I was going to stay right there in his life. It was a mother's need to know the truth," said Kraemer. "My goal was to push him to break. I wanted to break him."

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Marzo, 23, was last seen by friends walking into the house she shared with Rodgers in December 2003. She and three of her friends had enjoyed an innocent night out, a night frequently interrupted by Rodgers' urgent calls telling Marzo to come home.

"I was scared with her and Carl," said Kristina Randall, who drove Marzo home that night. "I was worried about what he could have done to her in the middle of the night."

Her friends had reason to worry because, they say, Marzo often showed up black and blue from the beatings she got from Rodgers.

"You could see her broken nose. It was swollen," Randall said. "You know, handprints on her arm."

"She walked in the house and I didn't even know it was my daughter. She was so beaten," Kraemer said. "And I remember pleading and praying that she'd never go back to this man."

While Marzo's mother is convinced Rodgers killed her, he had a simple explanation for his activities that night: He told his parents and his sister he threw Marzo out.

"Carl told us he found out she was hanging around with some people that he definitely wouldn't want around his kids or around his house," said Rodger's stepfather, Jeffrey Stemper.

"When people are in relationships, nobody can say what goes on behind closed doors," said Rodgers' mother, Anita Stemper. "Carl, my son, he's always been a sweet person, and I don't think that he's a monster, like these people are trying to portray him as."