An emotional time is at hand as the seaQuest's tour of duty comes to an end; Chief Crocker faces his retirement and the end of his marriage, Commanders Ford and Hitchcock are offered the same command, and Captain Bridger and Dr. Westphalen begin a romantic relationship. Most emotional of all is Lucas who realizes that his father is hardly a part of his life anymore. However, when the Earth's crust begins to crack open underneath his father's power plant, the world is threatened by an unstoppable rise in ocean temperature which will melt the polar caps. With lava seeping into the sea, Bridger must sacrifice the seaQuest in order to save the world.