WAUKESHA, Wis.- One of two Wisconsin girls charged with stabbing a classmate to impress the fictitious horror character Slender Man will plead guilty in a deal that calls for her to avoid prison time.

Fifteen-year-old Morgan Geyser will remain in a state mental hospital under an agreement announced Friday. It calls for Geyser to be evaluated by doctors who will report to a judge for a determination of how long she should remain in treatment.

Geyser and Anissa Weier were charged with attempted first-degree intentional homicide in the 2014 attack in Waukesha.

Weier pleaded guilty to a reduced charge last month. A jury later concluded she was mentally ill at the time of the crime. She faces at least three years in a mental hospital.

All three girls were 12 at the time.