One evening at The Bronze, Xander suavely saves the Slayer from a menacing vamp, then mounts the stage to play his guitar solo and "kiss her like she has never been kissed before." He is rudely awakened from this beautiful dream to find himself stuck in the hell known as biology class, and Dr. Gregory is about to call on him.
The only teacher who believes in Buffy, Dr. Gregory, is killed by a monster. The substitute teacher, Natalie French, turns every boy's head, and seems to have a thing about insects, especially the praying mantis. Buffy and Willow just roll their eyes.
Angel shows up at the Bronze, warns Buffy that somebody wants to rip her throat out, gives her his jacket, and vanishes again. Buffy's attraction to Angel becomes apparent when she wears his jacket at school. Cordelia finds the headless body of Dr. Gregory in the cafeteria locker. The Scoobies try to figure out if there is a connection to the Master, but don't rule out that there is a second monster about. Buffy goes into the park and confronts a vampire who has a large claw in place of a right hand. The fight is interrupted by the police, and the vampire flees. While in pursuit, she sees the vampire come up behind Miss French, who just stares at him. To Buffy's surprise, the vampire bolts in panic.
The next day, Buffy is sent to a counselor to help her get over seeing the dead body. This makes her late for the surprise test that Miss French gives the class Ã¢â¬â a test where she helps Xander with a question. Buffy looks through the window in the door, and Miss French turns her head 180 degrees to look at her. Later, Miss French asks Xander over to her house in the evening to work on a project.
Back in the library, Buffy figures that Miss French must be a praying mantis, and convinces the others. Buffy tries to warn Xander, but he brushes her off, saying that she is just jealous.
Miss French welcomes Xander with a drink, a fire in the fireplace, and a tight dress. The drink knocks him out just when she turns into an insect. Xander wakes up in a cage next to another student who tells him how she mates Ã¢â¬â deadly. Willow calls Xander's mother and finds out that he isn't home. Buffy gets Giles to record bat sonar, while Miss French chooses Xander to be her next victim. When the remaining Scoobies visit the house where Miss French is supposed to live, they find a nice old woman who is the real Ms. French, but retired in 1972. To quickly find Xander, Buffy tracks the one-handed vampire, who is so scared of the she-mantis that he knows just which house is the right one. Buffy breaks through the window when the mantis is about to mate with Xander. She slays the insect, using the bat sonar to weaken it.
Buffy, in Angel's jacket, later meets him at the Bronze. He tells her to keep it, and Buffy is obviously smitten. The last scene shows Buffy putting Dr. Gregory's glasses in his closet, but not noticing that there are she-mantis eggs attached to the bottom of a shelf.