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For a year, Theo “Sandy” Doan followed the instructions of an anonymous and mysterious person who left her text messages on her phone. The person demanded she drop money at locations around Dallas, and in exchange, he would keep quiet about a secret that could ruin her life.

Now, the mystery has unraveled. Doan paid $28,000 under the belief the person would not divulge an alleged affair with a 14-year-old student who took math in one of her classes.

It turns out the person who was demanding the money was the same student she allegedly slept with.

Now Doan, 27, and a middle school teacher, has been charged with having an improper relationship with a student and with sexual assault — a felony. She’s also been placed on administrative leave by the school district.

According to court records obtained by KDFW-TV, a Fox affiliate in Dallas, Doan admitted to having sex with the student three times in 2015, and the mysterious demands for money began soon after.

The boy’s mother became suspicious when her son had extra money — she believes he spent a lot of the cash on drugs — and would disappear for days at a time. The Washington Post reported that even as Doan made the payments, she continued her affair with the troubled teen, who has been in and out of the juvenile justice system.

The boy’s mother checked his cell phone and traced the text messages to Doan, according KDFW.