Captain Nemo and the Underwater City

Captain Nemo explains that the survivors will remain imprisoned beneath the ocean permanently. While the exact reason isn't fully detailed in the summary, Nemo appears to view Templemer as his own domain and vision for the future, offering Fraser a position in the city's development. The city is designed to be inescapable, with Nemo controlling all access and maintaining strict surveillance over the inhabitants.

Earlier, Joab warns that nobody has ever successfully escaped from Templemer, establishing the city's inescapable nature.

Lomax, the cowardly survivor, attempts to escape by stealing diving equipment. When that fails, he tries a more dangerous plan: rupturing the city's dome using the oxygen generator. However, his plan backfires catastrophically, flooding the control room and causing his own death.

During the city tour, Joab demonstrates how the oxygen and water production works, giving Lomax the knowledge needed to attempt his desperate escape.

Nautilus II explodes due to engine failure. Nemo specifically warns Fraser that there's a problem with the engines that could cause an explosion, but Fraser persists in trying to escape anyway. During the pursuit, the submarine crashes into a reef while still submerged, and the damaged engine causes the vessel to explode.

Nemo warns Fraser about the faulty engines during the chase, but Fraser ignores the danger in his desperation to escape.

Fraser's motivation is political. He confesses to Nemo that he's trying to prevent the supply of weapons to the American Civil War. He believes in a peaceful, slow approach to political change, even if it's more painful, and cannot accept Nemo's offer to join the underwater city's future. His sense of duty to the surface world compels him to risk everything for escape.

Fraser's earlier captivation with Mala's performance and Joab's notice of his fascination hint at his inner conflicts between staying and leaving.

Joab, Nemo's second-in-command, secretly assists Fraser and the Bath brothers in stealing Nautilus II. During the chaos of the explosion, Joab is electrocuted and confesses to Nemo that he helped Fraser escape before succumbing to his wounds. His motivation isn't explicitly stated in the summary, but his actions suggest sympathy for Fraser's political ideals or a desire to see the prisoners gain their freedom.

Joab notices Fraser's fascination with Mala's performance, hinting at his attention to Fraser's character and potentially his underlying sympathies.

Barnaby Bath drowns during the escape attempt aboard Nautilus II. When the submarine crashes into the reef and begins flooding, the crew attempts to evacuate through flooded compartments using diving gear. Barnaby panics in the chaos and drowns before he can escape, while his brother Swallow manages to survive.

The Bath brothers are established as thieves, and their desperate nature during the escape attempt aligns with their character traits.

Helena Beckett and her son decide to stay in Templemer despite the opportunity to escape. Helena admits to Nemo that she was aware of Fraser's escape plan but chose not to join it. Instead, she remains in the underwater city, suggesting she found acceptance or peace in her new life beneath the sea.

As a mother with her young son, Helena's priority appears to be stability and safety, which the city provides even within its confines.

Fraser declines Nemo's offer because he believes in working through legitimate, peaceful political channels to create change, even if it takes longer. In his farewell letter read by Mala, he explains that he cannot join Nemo's vision of the future because he must continue fighting for his cause in the surface world, specifically, working to cut off weapons supplies to the American Civil War.

Fraser's political role as a senator and his confession about the weapons supply establish his commitment to his cause over personal comfort.

Swallow Bath secretly hides a gold ladle under his coat during the escape. When Fraser and Swallow are rescued by the schooner on the surface, they share a knowing, remorseful smile. Fraser tosses the gold ladle into the sea, symbolizing their rejection of greed and their past criminal lives, a deliberate choice to leave their old ways behind.

The city's waste of gold is highlighted during the city tour, where Joab shows them the precious metal being discarded carelessly, establishing gold's strange abundance in Templemer.

After Nautilus II crashes and explodes, Fraser and Swallow Bath somehow reach the surface and are rescued by a schooner in mid-ocean, far from land or any wreckage. The exact mechanism of their survival isn't detailed, but they manage to escape the doomed submarine before the explosion and swim or float to the surface, where they're spotted and rescued.

The pursuit ends with Nautilus II crashing into a reef while still submerged, and the crew attempts to evacuate through flooded compartments using diving gear.

Mobula is a massive manta ray-like beast that was unintentionally created during the construction of the underwater city. During Fraser's training on Nautilus II, he accidentally rams and kills the creature while learning to operate the submarine. This incident showcases the dangerous and unpredictable environment beneath the city, as well as the unintended consequences of Nemo's scientific endeavors.

The city's tour reveals the advanced technology used to build Templemer, suggesting such experimental creations are possible.

Nemo pursues the stolen Nautilus II in the original Nautilus, attempting to catch up and prevent their escape. However, despite his warnings about the faulty engines and his attempt to go beneath a reef to escape, the pursuit ends in disaster when Nautilus II crashes into a reef and explodes. Nemo arrives too late to save anyone, witnessing the destruction of the stolen submarine.

Nemo warns Fraser about the dangerous engines, showing his attempted intervention before the tragedy occurs.