Due to rampant clouds of so-called unstable magic -- which have unpredictable effects on everything they contact, but usually result in death for any humans caught in their wake -- humankind has devolved into a society of loosely-knit communities. A few spells have been discovered which can discourage the unstable magic for a time, but not banish it entirely.

An aging printress, Maisie, is responsible for churning out thousands of spell sheets each season for the communities in her area. Aided by her husband Velar, she does her best to stave off her inevitable replacement, though she worries this latest season might be her last.

As it happens, the deadline for completion of this season's spells coincides with her fiftieth birthday. Maisie's children are planning to make the dangerous journey to Maisie's community to celebrate with her. But they are late. Worryingly late.

To save their children, Maisie and her husband harness up their old dog sledge team. They pack dozens of copies of the spell sheets known to keep unstable magic at bay. They race to find (and save) their children before they can fall victim to the whims of the unknowable mist. And they relearn a truth they'd forgotten: one is never too old for an adventure.