A man from Springfield, Mo., has agreed to plead guilty to charges that he took a 17-year-old girl from Massachusetts to Rhode Island with the intent of selling her for sex. Authorities said Stephen Ardrey, 30, took the developmentally delayed girl from a library in Medfield, Mass., in September. She was found a few days later in Coventry after someone saw her walking with Ardrey. Ardrey was arrested and has been in federal custody since then. In a plea agreement entered this week in federal court in Providence, Ardrey agreed to plead guilty to trafficking a minor and transporting a minor to engage in sex. He is scheduled to be arraigned Tuesday.