An ancient cataclysm has sundered a medieval world into two parallel dimensions. An order of monks struggles to keep the two lands united by building portals - complicated, expensive, temporary, and above all dangerous contraptions that can slice your arm off as easily as they cut through reality.

Three families converge on the engineering secrets that will create a miracle:

A genderless pair of small-town priests are forced into the deadly political machinations of their merchant Church, who controls the portals.

A family of rogue portal-makers is driven to starvation by the Guild that safeguards their riftmaking secrets.

An orphaned eight-year-old, forced to crawl between the worlds by a mad merchant, stumbles into a dimension-spanning conspiracy.

This is the spellbinding, epic, low-fantasy tale chronicling the decades-long construction of the great mechanism that will bridge these severed worlds - the fabled Cathedral of Portals.