Her desperate plea led to the arrest Sunday in Chicago of her husband, a 32-year-old Rockford, Minn., man. The Associated Press does not generally identify victims of sexual abuse and is not naming the man to avoid identifying his wife.
The man's arrest comes after Craigslist promised last year to screen all submissions to its "adult services" section before posting them. Dart and other law enforcement agents have repeatedly accused the online site of promoting prostitution in its ads.
In the latest case, the woman told investigators her husband regularly posted ads, promoting her for sex. She claimed he would arrange the encounters, then demand she immediately deposit the money she was paid into his bank account.
He was arrested at a downtown Chicago hotel when he arrived with the child to pick up his wife after what he assumed was her weekend of prostitution.
The man controlled his wife with threats to their child, convincing her she would never see their preschooler again if she didn't take part, Dart said.
"He used the threat of the child being kept away from her forever," Dart said. "They were legally married, her at a very young age. He had been some type of counselor to her at one stage when she was young. At some point, they had the child."
Rockford, population 4,000, has a small-town feeling even though Minneapolis is less than an hour's drive away. The town sits on the Crow River, surrounded by rolling farm fields and subdivisions. Headline-grabbing crimes are rare.
The man faces a felony charge of pandering and is being held on $150,000 bond. It isn't clear whether he has an attorney.
The woman and the child were being kept at a safe location. Dart said the woman hasn't been charged with any crime, but "that's being examined."
Authorities said the man had been in touch with his wife all weekend, arranging encounters for her. She told him she was sick and wasn't turning all the tricks he'd set up. The man then drove to Chicago to confront her, authorities said. Investigators followed the man after he left Florida, where he'd forced his wife to work last week.
Dart said his department has "had a long tortured relationship" with Craigslist. Last year, he filed a lawsuit alleging the Web site had become the "largest source of prostitution in America." A judge dismissed the lawsuit.
Craigslist CEO Jim Buckmaster reacted to the arrest Wednesday in an e-mailed statement to The Associated Press.
"Criminal exploitation is reprehensible, and craigslist works with law enforcement when called upon to apprehend and prosecute those responsible," Buckmaster said in the statement. "Misuse of craigslist for criminal purposes is extremely unwise, since an electronic trail to the perpetrator is inevitably created."
He didn't comment on the specifics of the Chicago arrest.
Associated Press Writer Martiga Lohn contributed to this report from St. Paul, Minn.