Kit has been obsessed with Mars lately, and has been spending a lot of time there. Often that time is with Ronan and Darryl, because Nita doesn't share his fascination with the red planet. Yet there's a real wizardly mystery on Mars: its kernal is missing. This could have real and unpredictable consequences, and there's also the question of why there aren't any Martians. So the boys aren't there alone; quite a few other wizards, including Earth's Planetary, Irina, and the regional Species Archivist, the saurian Mamvish, are also studying Mars.
Meanwhile, Nita is juggling her own set of issues. Younger sister Dairine is spending most of her time on Welkath, studying star management, and their father wants Dairine to at least check in more regularly. Since he can't follow her and bring her back for meals, chores, and the last few days of the school year, Nita has to.
She's also juggling her own changing feelings for Kit, and since she has no idea whether he will feel the same way, or whether it will just mess up their wizardly partnership, she's just as glad to not be spending too much time with him right now.
When Kit finds an apparently ancient, and wizardly, artifact on Mars, though, things start to change. Despite a formal decision by Irina and Mamvish to leave the artifact be while there's more study and analysis, Kit and his buddies go back to take another look on their own, and Kit stumbles onto the means of opening it--and things start to happen on Mars.
A whole lost civilization, and species, has been in stasis on Mars for over half a million years, waiting for a chance to come back and restore Mars to habitability for themselves. They need Mars' missing kernal, though, and to retrieve it, they need Kit's help.
It isn't at all clear that this is good for Kit, or for humans generally, or even for Mars.
Meanwhile, Kit's sister Carmela, who is not a wizard, is using her unintended introduction to wizardry and to galactic civilization to pursue a career as a galactic personal shopper, and their other sister, Helena, who thinks Kit has made a deal with the devil, is returning home unexpectedly quickly after the end of her college term.
Everything is spiraling toward about fifty different kinds of disaster
This is another great Young Wizards romp, well worth your time if you've enjoyed previous installments. Recommended.
I bought this book.