Amanda has been a British witch for twenty years or more. You wouldn't think it to look at her -- she's a pretty, dark-haired young mother of two teenagers, happily married to a compliant husband who doesn't mind her going off with little notice to handle affairs of her witchcraft circle. When the novel begins, she's also got her sister Zillah living with her, along with Zillah's young son Marcus.
Her husband is not aware, though, that his wife is a member of the Inner Circle of Britain's witches --the Ring. When the novel begins, she and the others of the Ring are just discussing the problem that one of their members, Mark Lister, has become aware of -- a universe of pirates who are somehow draining Earth of energies, and also sending Earth a series of problems, some very serious, which are terribly difficult to solve.
Eventually the group decides to send a group of fighters with magical talents to the other universe to undermine the pirates in whatever way seems bet to them. Amanda takes on the task of seeing to it that a vessel is built for the journey, and her colleague -- redheaded, freckled temptress Maureen -- takes the lead in selecting those who will take part. Meanwhile, Mark continues to use his computer skills to calculate launch times and orbits, while Gladys sets things in motion to build power from the rest of British witchcraft circles, including many other groups who think they are participating in something entirely different.
After the launch, however, Amanda learns that her sister and Marcus have disappeared, with no news on why or where they've gone. She calls Gladys in a panic, and Gladys does some farseeing, only to learn that the two have gone along on the anti-Pirate mission. And as far as anyone knows, it's a one-way mission for all concerned.
The action soon moves to follow the pirate-bashing squad, and Amanda is left behind. She only turns up again when her circle, complete except for Gladys, is frantically trying to find out what to do next, and Amanda is called on to balance magical forces while Zillah, present only as a ghost, tries to do the one thing that will undermine the one person who threatens everything and everyone she loves.
Luckily, Amanda is enough of an accomplished witch and a loving sister to do exactly what is needed, and things turn out well in the end.