Updated

A Missouri man accused of torturing a young woman he kept as a sex slave pleaded guilty Tuesday to having sex with her when she was underage, but more serious charges including sex trafficking were dropped.

Edward Bagley, 45, had been facing 11 federal charges accusing him of enticing an underage girl to be his sex slave, torturing and mutilating her, and allowing others to view the torture sessions either in person or over the Internet. Instead, Bagley, known as "Master Ed" pleaded guilty to one count of using an interstate facility to entice a minor into illegal sexual conduct and agreed to a 20-year prison sentence that still must approved by a federal judge.

The victim was 16 in 2002 when she moved into Ed and Marilyn Bagleys' trailer and on the outskirts of Lebanon, a rural community 140 miles southeast of Kansas City, prosecutors said. She lived with them until early 2009, when she was taken to a hospital in cardiac arrest at age 23 after what prosecutors said was a torture session.

Bagley's attorney, Susan Dill, had contended that the woman was 18 when she voluntarily started engaging in extreme sexual acts with Bagley as part of the bondage, discipline, sadism and masochism lifestyle, and that Bagley did not have sex with her while she was a minor.

Former U.S. Attorney Beth Phillips has called the case one of "the most horrific ever prosecuted in this district."

According to Tuesday's plea agreement, Bagley met the woman when she was 16 and dating his teenage son and knew that she had suffered emotional, physical and sexual abuse in her past. Bagley provided her with her own room, clothes and promised her a great life, the agreement says, and taught her about BDSM activities using images and videos from the Internet.

Also as part of the plea deal, Bagley admitted to engaging in bondage acts with the woman that included the use of needles and skewers, whipping and electrocution.

Prosecutors and defense attorneys declined to comment.

Four other men have pleaded guilty to conspiracy charges, admitting they engaged in or watched the sexual torture of the woman at the Bagleys' home.

One of those men, Bradley Cook of St. Louis, entered a plea bargain that includes a 20-year sentence. Dennis Henry of Wheatland also pleaded guilty of transporting the victim across state lines for sexual activity and could face up to 15 years, while Michael Stokes of Lebanon, Mo., and James Noel of Springfield are facing five years on the conspiracy charge.

Bagley's wife, Marilyn, pleaded guilty to conspiracy and will be sentenced to probation under her plea deal.

None of those five have been sentenced.