Mankind is shaping the Long Earth - but in turn the Long Earth is shaping mankind ...

A new 'America', called Valhalla, is emerging more than a million steps from Datum Earth, with core American values restated in the plentiful environment of the Long Earth - and Valhalla is growing restless under the control of the Datum government... Meanwhile the Long Earth is suffused by the song of the trolls, graceful hive-mind humanoids. But the trolls are beginning to react to humanity's thoughtless exploitation ...

Joshua, now a married man, is summoned by Lobsang to deal with a gathering multiple crisis that threatens to plunge the Long Earth into a war unlike any mankind has waged before.