From the story Ocean of Night, the submarine Barracuda has survived a trip through the farpool-wormhole on Europa, emerging into the oceans of a water world thousands of light years away, a place called Seome. The crew eventually understands that Seome is the ancestral homeworld of their fish people.

Brief exploration reveals that Seome, as is Europa, is rich in fusium resources, a byproduct of the local life known as seamothers. Fusium is critical to the economy of the late 22nd century. But the growing conflict between the two alliances that dominate the solar system, the Inner Federation (InFed) and Concordance, has now also come to Seome.

Original Europa settler Cameron Meyer is increasingly horrified at the prospect of InFed exploiting the seamothers and wrecking Seome as they have Europa and other moons of Jupiter. To slow down this overdevelopment and protect the serpents, she has been covertly feeding details of InFed's plans to contacts inside Concordance. But her efforts are beginning to cause increasing problems with her family and friends as she finds herself drawn deeper and deeper into a web of deceit, espionage, sabotage and treason.

On Europa, indigenous seamothers are fleeing the teams hunting them, through the wormhole at the bottom of the Europan ocean. To the surprise of everyone, the serpents begin to demonstrate intelligent and aggressive behavior toward humans. Building a makeshift explosive device made of fusium, the few remaining serpents detonate the device and destroy the local infrastructure, including the farpool-wormhole.

Now, the InFed and Concordance teams on Seome are trapped there, with no easy way to return to Europa. The conflict turns into open warfare and Cameron's father Ethan is killed in an attack. Finally, recognizing their situation, the two adversaries call a truce and agree to cooperate on engineering a new man-made farpool-wormhole. Conflict flares again when the Concordance commander insists that the gateway will not 'land' on Europa but at a new base well inside Concordance space, in fact on Pluto.

The effort to engineer a new wormhole and escape Seome becomes a race against time, as observations show that Seome's sun, Sigma Albeth B, will soon reach a supernova state. Ultimately, the two teams are forced by events to use an untested wormhole to survive the coming cataclysm.

At the Concordance Pluto base, Cameron and her teammates are taken into custody. Despite efforts to hijack a Concordance ship and return to Europa, the teenagers approach their home world only to be intercepted and ordered to prepare to be boarded.

Now a decision must be made: try to flee capture or allow themselves to be taken prisoner again.

It will be the most difficult decision they have ever made.

Second book in the trilogy Tales of Europa.