As climate disasters wreak havoc, a sister and brother take opposing sides on the fate of the human race.

Syrah Carthan wants to save it. A tour guide for the Sequoia National Park, Syrah has an affinity for the millennia-old giants that extends to Rhiza, a subterranean world as ancient as Earth itself. Syrah is the reluctant heir apparent as its Keeper. Her duty is to maintain a balance between nature and humans. But Syrah's greatest adversary has his duty as well.

Romelo, Syrah's brother, wants humankind to get what it deserves. To protect the forests, he's already instigated one battle that ended in chaos and death. To reverse the near extinction of the magnificent trees, Romelo's next move is to conspire with the sequoias themselves. If all goes according to plan, it will leave human beings absolutely breathless.

The siblings are going to battle. In the worlds above and below, only one of them can emerge victorious.