It's 2045-2059. After the cataclysmic upheavals of Step Day and the Yellowstone eruption, humanity is spreading farther into the Long Earth, and society, on a battered Datum Earth and beyond, continues to evolve.
Now an elderly and cantankerous AI, Lobsang, lives in disguise with Agnes in an exotic, far-distant world. He’s convinced they’re leading a normal life in New Springfield - they even adopt a child - but it seems they have been guided there for a reason. As rumours of strange sightings and hauntings proliferate, it becomes clear that something is very awry with this particular world.
Millions of steps away, Joshua is on a personal journey of discovery: learning about the father he never knew and a secret family history. But then he receives a summons from New Springfield. Lobsang now understands the enormity of what’s taking place beneath the surface of his Earth - a threat to all the worlds of the Long Earth.
To counter this threat will require the combined efforts of humankind, machine and the superintelligent Next. And some must make the ultimate sacrifice....