They are greeted by Atmir and his Guardians who promise to take them "to safety". En route, Greg, Charles and the others are told by Atmir that Atlantis is not just one city, but seven cities, the first two of which have been "lost beneath the waters of the outer limits forever" and the third one, Troya, is now deserted and empty.
Atmir takes the surface-dwellers through the causeway, a prehistoric swamp inhabited by the Mogdaan, and then on to Vaar, the fourth city.
Once here, Greg and the others are thrown into a dungeon were they make friends with Briggs, the captain of the Mary Celeste and unofficial leader of the Atlanteans' human slaves, and his daughter, Delphine. Briggs informs them they are to be slaves to protect Vaar from the constant attacks of creatures known as Zaargs.
They will be given gills so they can never leave Atlantis and return to the oxygen-rich surface world, as the Atlanteans, being originally from Mars, breathe a different atmosphere. A convenient Zaarg attack allows Greg and the others to escape from their cell, but also claims the life of Briggs eaten by a Zaarg.
They steal some rifles the Atlantians have acquired from a ship they plundered and retrace the route they took through the causeway when being brought to Vaar.
Quite a seat filler in it's day - but surely these Atlantians must have been plundering ships for hundreds of years... So Atlantians/Pirates whose to say... cue a small project...
These will give me something to do whilst I prep more Napoleonics for the Ottoman project.