A junior overachiever who joins Dash in the school archives searching for a confiscated cell phone. She is placed in detention with him and later becomes part of the core group navigating the sinking school floors to reach the roof for rescue.
Their shared punishment becomes the basis for cooperation during the sinking.
Dash and Mary are thrown into detention together after breaking into the school archives.
Grimm represents the school authority whose failure endangers Mary and the other students.
As principal, Grimm oversees the school while Mary is a student navigating the disaster caused by the unsafe auditorium.