NILES, Mich. -- There is a surprise twist on in the Niles "sextortion" case!

Trey Nichols pleaded guilty to two charges Tuesday morning -- including sexual assault.

He is one of five Niles teens accused of blackmailing a girl into sex by threatening to post a sex tape on Facebook.

Nichols was set to go to trial next month, but the prosecutor told us he changed his mind late Monday night, and decided to take a plea deal.

Nichols will be sentenced January 12.

The big question now: Will the last co-defendant in the Niles "sextortion" case cop a plea?

Martell Miller will be back in court on Wednesday.

He refused a deal on Monday, so the judge set a trial date.

On Tuesday, his lawyer requested another meeting with the judge and the prosecutor.

Right now, Miller set to go trial next Tuesday.