The elevators connected Earth to the stars. The towers suppressed the deadly plague. As the final Builder event approaches, five keys will unlock their secret.

After discovering the first key in the wreckage of a crashed Builder ship, Skyler Luiken and his crew follow the migrating aura towers in search of the four remaining relics. But time is running out: the survivors learn that the next Builder event will be the last, and one of the objects has already fallen into dangerous hands…

As the alien Key Ship looms above Earth, and the surface below is ravaged by corrupt councils, fanatical cults and infected subhumans, the team race to retrieve the missing artefacts.

Will they finally reveal the Builders’ plan?