The last surviving Mothertrees are under threat. Without the Reachers, those with the ability to restore them to health, they will die and the children of the Reachers will remain frozen in a state of perpetual childhood.
Walde, a Reacher who is fighting against the odds to save one of the last remaining Mothertrees, now discovers that he will soon become a father and becomes fixated on protecting it, since he is well aware that his child will not grow if it dies.
To that end, he gathers a disparate group of Reachers and others who have learned the true value of the Mothertrees to their continued existence and as their sole point of contact with Thara, an enigmatic but powerful being who lives deep in the earth.
With this determined band, Walde wages a defense against those who are ready to destroy them, prepared to do whatever it takes to protect a way of life stretching back thousands of years.
But how far is too far? And how much of himself will he have to sacrifice to achieve his goal?