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 super-intelligent Next.

And some must make the ultimate sacrifice . . .