In 1883, as Krakatoa roars to life with relentless eruptions, the safety of a mission school in Palembang on nearby Sumatra becomes a desperate concern for everyone who crosses its shadow. On the steamer Batavia Queen, Captain Chris Hanson [Maximilian Schell] leads a diverse group of passengers toward Krakatoa’s volatile coastline, bringing together a mix of daring adventurers and troubled souls. Among them is Laura Travers [Diane Baker], who has a painful secret she hopes to keep hidden: her past marriage to an abusive husband and a son named Peter, whom she believes may still be alive somewhere after the Arianna, the pearls, and the tragedy she endured in Batavia. Also aboard are Douglas Rigby, the practical owner and operator of a diving bell, and his accomplice in danger, the air-charmed divers Giovanni and Leoncavallo Borghese [Rossano Brazzi], whose ballooning dreams brush shoulders with fate. By Hanson's side are the grizzled diver Harry Connerly [Brian Keith] and Connerly’s devoted partner Charley Adams [Barbara Werle], as well as a quartet of Japanese pearl divers led by Toshi [Jacqueline Chan], whose quiet determination belies the peril around them.
From the outset, Hanson’s voyage is not merely a search for salvaged pearls or a missing boy, but a fragile attempt to balance personal history with professional duty. Laura Travers carries the weight of her past as the Arianna’s trail becomes part of the present, while the crew suspects the truth or fiction of her tale about the pearls. A colonial official warns that Krakatoa’s sea and sky roil with danger, yet Hanson presses onward, intent on the mission’s dual aim: recover the Arianna’s pearls and locate Peter if he indeed survived. The Batavia Queen is soon joined by a grim addition—the 30 convicts and their jailer, a last-minute transport that casts a shadow over every decision made aboard.
As the voyage unfolds, the ship’s passengers witness a series of uncanny phenomena: seabirds gathering in unusual flocks, bursts of fiery explosions from the sea, and a peculiar, piercing hiss like escaping steam. Danzig—Lester Danzig [J.D. Cannon]—emerges as a troubling presence, and he discovers a hidden truth about Connerly’s lung disease, a truth that could threaten the very diving work that anchors the voyage. He uses this knowledge to manipulate the situation, creating tension among Hanson, Laura, and the others. The Borgheses, Connerly, Charley, Toshi, Rigby, and the other passengers face a debate over trust and truth as the ship closes in on Krakatoa’s ominous plume.
The Batavia Queen finally nears the eruption-scorched coast, where the Borgheses’ balloon lifts them toward the smoky island and Rigby descends in his diving bell to inspect the wreck of the Arianna. The search is perilous: a faulty engine and a hazardous descent threaten the crew’s already fragile security. In the ensuing chaos, Danzig seizes a pistol and frees the prisoners, seizing control of the hold as Hanson and his allies scramble to restore order. Yet even as the mutiny rages above, Hanson discovers a critical clue in the Arianna’s safe—no pearls, only a cheap pocket watch—an apparent dead end that sharpens the crew’s resolve to uncover the truth.
A new lead emerges when Hanson, aided by Rigby, frees the remaining divers and uncovers the Arianna’s logbook, which reveals a port call at Palembang before the ship sank. A letter tucked into the logbook confirms that Peter had disembarked there to attend the mission school. The pursuit shifts from the sea to Palembang, with Krakatoa’s fury intensifying around them. Toshi falls victim to a lava bomb, a stark reminder that time is running out. The Batavia Queen presses toward Palembang and discovers the mission school badly damaged but still functioning, its staff and students rescued from a sinking sampan.
Peter’s reunion with Laura brings a moment of relief and hope, and a chest belonging to Peter is brought aboard the Batavia Queen—inside lies the missing pearls, ensuring that Connerly, Rigby, the Borgheses, and the surviving divers receive their rightful shares. Yet the sea’s cataclysm is not finished. Krakatoa’s eruptions intensify, and Hanson braces for a potential tsunami, seeking to keep the ship safe while reluctantly allowing some passengers to seek faster safety ashore. In a tense turn, Giovanni Borghese, Charley, and the three surviving pearl divers join Connerly in a lifeboat bound for Anjer, weighing their odds against a looming disaster.
The volcano’s culminating blast unleashes a monumental tsunami that slams into Anjer. The Batavia Queen and its lifeboat-based refugees ride out the wave, but not all who hoped to survive do so. Connerly and Charley perish in the deep, embracing one last time as the sea takes them. In the wake of the devastation, Hanson, Laura, Peter, Rigby, Leoncavallo Borghese, and the ship’s crew cling to life on the Batavia Queen, their bond reinforced by shared danger and hard-won fortune. What began as a perilous voyage—a search for wealth, a struggle for truth, and a fight for survival—ends with a hard-won rescue and a hard-earned future for those who remain aboard the battered vessel. The sea that brought them together does not release its hold easily, but it grants a fragile redemption to those who endure the final, towering reshaping of Krakatoa’s memory.
