During a routine inspection following a relatively-minor and apparently-uneventful earth tremor along the coastal fault-line north-west of the Bay of Naples, a maintenance team ventures into the deep foundations of a deserted site awaiting redevelopment, ostensibly to perform safety checks on the integrity of the substructure. What they find suggests the tremor was more powerful than at first suspected and the partial destruction of the lower levels has opened up an extensive gallery leading to the centre of the city and, ultimately, a place thought to no longer exist. As part of an extended field-trip to gather information for the university where he is a part-time lecturer in the classical antiquity of the Mediterranean, Werner and his new wife, Sophie, gain access to the site under the auspices of the recession-hit Garcia construction group where they retrace the steps of the inspection team. As they progress further and further into the maze of cavernous foundations and supporting structures they come across what appears to be the abandoned and virtually-intact remains of a major Roman underground water cistern and distribution station. Was it financial constraints or the decline of the western empire or something infinitely-more sinister that prevented completion of the project? Within the dark and eerie confines of the subterranean depths, Sophie and Werner seek out evidence of another time when they were known to each other but are soon plunged headlong into their former world when the abandoned workings divulge their deadly secret.
