Something stopped Nita's hand as it ran along the bookshelf. She looked and found that one of the books had a loose thread at the top of its spine. It was one of those So You Want to Be a . . . books, a series on careers. So You Want to Be a Pilot, and a Scientist . . . a Writer. But this one said, So You Want to Be a Wizard. I don't belive this, Nina thought. She shut the book and stood there holding it in her hand, confused, amazed, suspicious—and delighted. If it was a joke, it was a great one. If it wasn't? .

Nita and Kit return from their wizardly holiday, looking forward to getting back to their everyday routine. But there's trouble brewing. A strange darkness of the mind and heart is about to befall the older wizards of the world, stealing away their power. Soon, the young wizards of Earth and many other planets find themselves forced to defend wizards and nonwizards alike against an invasion of a kind they've never imagined.

But mere defense won't be enough to combat the evil afoot. With their alien teammates, Nita, Kit, and Dairine must race to search worlds known and unknown for the secret weapon the Powers That Be have promised them--before the minions of the sinister Lone Power find it first. And then, for the first time in millenia, the wizards must go to war. . . .

Every eleven years, Earth's senior wizards hold the Invitational: an intensive three-week event where the planet's newest, sharpest young wizards show off their best and hottest spells. Wizardly partners Kit Rodriguez and Nita Callahan, and Nita's sister, former wizard-prodigy Dairine Callahan, are drafted in to mentor two brilliant and difficult cases: for Nita and Kit, there’s Penn Shao-Feng, a would-be sun technician with a dangerous new take on managing solar weather; and for Dairine, there's shy young Mehrnaz Farrahi, an Iranian wizard-girl trying to specialize in defusing earthquakes while struggling with a toxic extended wizardly family that demands she perform to their expectations.

Together they're plunged into a whirlwind of cutthroat competition and ruthless judging. Penn's egotistical attitude toward his mentors complicates matters as the pair tries to negotiate their burgeoning romance. Meanwhile, Dairine struggles to stabilize her hero-worshipping, insecure protégée against the interference of powerful relatives using her to further their own tangled agendas. When both candidates make it through to the finals stage on the dark side of the Moon, they and their mentors are flung into a final conflict that could change the solar system for the better or damage Earth beyond even wizardly repair.