Cynthia returns from a semester in Europe and is moody. Malcolm discovers it's because she developed big breasts, which soon gets Reese attention thanks to Malcolm accidentally revealing the truth and he comes up with an elaborate plan to seduce her.
Meanwhile, Lois's friend Karen is sober and tells her she kissed Hal on New Year's, which causes tension as Hal repeatedly denies it. Dewey teaches Hal how to fly a kite and Francis becomes obsessed with a totem pole.
"Cynthia's Back" provides examples of:
- Armor-Piercing Question: Malcolm exposes Reese's plan by asking this: "What's her name?"
- D-Cup Distress: Cynthia's moody attitude is because of her developed breasts.
- Language Equals Thought: Invoked and Averted. An annoyed Inuit man tells Francis that he has only one word for snow.
- No-Holds-Barred Beatdown: Cynthia gives Reese this when he makes a desperate final attempt at her breasts, knocking him down with one punch before brutally kicking him on the ground as she goes on a monologue on how she should be treated with respect.
