Successful at delivering the cure for the Second Great Plague to the Land Dwellers, Allie and Dylan return to Oceania. But their rogue actions have cost them dearly. For disobeying direct orders from Mayor Cho, Dylan and Allie are exiled to a remote scientific research station in the Mariana Trench called Shark Station. Located in the second deepest part of the ocean—Sirena Deep—they are thousands of miles away from their beloved city. Accompanied by five adults who ensure that they work hard to run the old station, they’ve resigned to their fate. Yet mysteries of the deep are about to surface and the Sirena Deep may prove to be more dangerous than they ever could have imagined.