Xander saves Buffy from a vampire at The Bronze. He plays music on an electric guitar and she is captivated. In reality, this is a dream; he is daydreaming during his biology class.
The biology teacher gives Buffy encouraging support to be a better student. Something attacks him when he's alone in the class.
Blaine, an egotistical player at Sunnydale High, brags about scoring on women and questions Xander's manhood. Xander asks Buffy and Willow to back him up until Buffy talks to a familiar face.
Angel gives Buffy his jacket to keep warm.
Buffy and Willow worry about the missing biology teacher. Xander is captivated by the new substitute teacher, Natalie French. She gives a lesson about the praying mantis and asks her students to help with creating mock egg sacks.
Cordelia discovers a headless body in the cafeteria fridge. The body belongs to the missing teacher.
The Scoobies believe the death isn't due to a vampire. Buffy heads out in search of a knife-wielding vampire as the potential cause of the death. However, when they go after Miss French, the vampire runs away in fear.
Principal Flutie forces Buffy to visit a guidance counselor. She misses a pop quiz in biology but sees Miss French turning her head completely around on her body.
Miss French invites Xander back to her place after school to create the egg sacks. She eats a sandwich filled with bugs.
Buffy is positive that there is something off about Miss French. She thinks her teacher is a giant praying mantis. Buffy warns Xander not to go after Miss French, but he disregards her warning.
Xander visits Miss French's place and he drinks a martini. She makes a move on him before her arms transform into insect form. He's held prisoner and finds Blaine locked in the next cell.
Giles learns from an old acquaintance that the demon is a "She-Mantis" and lures innocent virgins to their deaths.
The substitute records lead the Scoobies to the wrong address; Miss French is pretending to be a retired teacher. Buffy traps the knife-wielding vampire and uses him as a tracker to find Miss French's house. She kills the vampire when he fights back.
Buffy uses bug spray to fight about the insect. A bat sonar is used to distract Miss French in time for Buffy to kill her. Xander attacks the eggs to eliminate all of her babies.
Back at the Bronze, Angel bumps into Buffy again. She offers to give back his jacket, but he tells her to keep it.
A few of Miss French's insect eggs are hiding away in the science classroom.