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

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

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

The girl, who is not identified in police filings, was beaten when she didn't follow the couple's directions or complete her chores, according to police. The girl said the abuse went on repeatedly 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, the arrest affidavit said.

Police said 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.

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. A call to their home Wednesday went unanswered.

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