Rescued from a dying planet, Barry Saint-Albans, the second-greatest detective in all the universes, is given a simple task: track down the missing son of the captain of a belligerent star ship that is threatening the Inn of the Sixth Dan on the very edge of uncharted space.

Unfortunately, said son has joined a procession of pilgrims heading off into the unknown in search of peace, answers to why we are all here, and where we came from before everything went pear-shaped.

None have ever returned to tell.

Barry is tasked with finding out what has happened to the missing travellers, with a restricted time frame and instructions to bring back the missing son alive, dead or in gaseous form, before the inn is destroyed.

The trail takes him into a preposterously populated unknown, through a frontier settlement, a tax haven for despots and oligarchs, an exile planet for road planners and a Stone Age society run by an old enemy (or at least one of his cousins).

The ultimate answers are revealed, but will they be enough to prevent Barry meeting the same fate as the pilgrims, and the Inn ceasing to be, and how does this all fit in with the killing of the ruling family in a devastated star system back home?