A novel by Diana Wynne Jones
. A team of mages finds it necessary to invade an alternate universe.
- Baby Talk: Marcus, Zillah's son. Rather well educated and smart even though his words hardly make sense to anyone but Zillah.
- Blithe Spirit: All of the women who go to Arth.
- Elseworld: Earth, Arth, and Petarchy. They even have alternate people called Analogues.
- Everything's Better With Ether Monkeys: Jimbo
- Henpecked Husband: Mark tends to question from time to time why he married Paulie.
- I Choose to Stay: After the congo dancing scene, the women decided to stay in Arth
- The Infiltration: What drives the plot; realizing that another world has been forcing Earth into war after war to force them to build new technology and copy it, Gladys sends a team of highly trained female mages (as well as Zillah, by accident) to the other world and stop them.
- The Load: Roz tends to see Zillah as this.
- The Mole: Brother Tony is assigned to spy on Paulie and return information to Arth. Later, because Tod kissed Zillah, he has to fill in, much to his displeasure.
- Never the Selves Shall Meet: When they enter the alternate universe, all the ones with counterparts there instantly die.
- Shrinking Violet: Zillah again.
- Sex Is Evil: In-universe. It's not allowed in Arth because it will upset the balance.
- Eccentric Mentor: Gladys
- Tomato in the Mirror: Mark.
- Wild Magic: Zillah's true potential