A South Florida couple allegedly turned a teen into their sex slave and sealed her off from the outside world for more than five years, police said.

Rob Johnson, 44, and his wife, Marie Johnson, 43, of Port. St. Lucie, were arrested on Tuesday and charged with felony sexual assault.

The Port St. Lucie Police Department said the girl was sent to live with the Johnsons at age 13 after her mother died, and was told she could only be part of their family if she agreed to have sex with them. She was told to call Rob Johnson “master,” investigators said in an arrest affidavit, and Marie Johnson pushed her against a wall and held her by her throat until she agreed to the sexual demands.

The girl, who isn’t identified in police filings, was beaten when she didn’t follow the couple’s directions or complete her chores. The girl said the abuse continued for more than five years. All the while, Rob Johnson held Sunday school classes for his family at their home, invoking Old Testament passages to justify the actions, according to the arrest affidavit.

The girl, now 21, was homeschooled, not allowed to use the phone and forced to rehearse what to say to doctors if she was asked about sexual activity, according to police.

The girl eventually was able to leave the home after her grandmother purchased a plane ticket to bring her to Ohio, the police said.

The Johnsons were freed on bail later Tuesday, the St. Lucie County Sheriff's Office said, after each posted $60,000 bond. No attorney was listed for them.

Port St. Lucie is on Florida's Atlantic coast, about 115 miles north of Miami.

The Associated Press contributed to this report.