The Phantom from 10,000 Leagues

One evening, a fisherman rows out to Baker's cove, off a beach in California, and is killed by a mutated sea creature guarding a mysterious light source coming from the ocean floor. The man's charred body is discovered by William Grant, an investigator for the U.S. Department of Defense, and marine scientist Dr. Ted Stevens. Unknown to Grant, Stevens has been assigned to work undercover on the case, as two other men have already been killed by the monster, which locals call "the phantom." Using the name Ted Baxter and pretending to be a tourist, Ted is offering to help Grant when they are interrupted by George Thomas, who is lurking in the shadows. Thomas, the assistant of oceanographer Prof. King, who works at the nearby Pacific College of Oceanography, claims that he was searching for specimens. George actually was following King, who had been the first to discover the body before hurrying away, but Grant believes George's lie. Ted then goes to the King home, where King has instructed his daughter Lois to assert that he has been home all evening, even though he just came in. King, who has been worrying Lois with his peculiar behavior, then climbs out his bedroom window before Ted can talk with him. The next day, King's secretary, Ethel Hall, chats with janitor Andy, who tells her about the most recent killing. Andy is suspicious of King, who has been working in great secrecy lately, but Ethel dismisses his concerns. Ethel is also desperate to discover what King is working on, and after King enters his locked laboratory, she retrieves a piece of paper that he dropped. George snatches the paper away from Ethel and alternately tries to bribe and threaten her in order to gain her help in accessing the lab. Meanwhile, Ted makes a test dive in the cove, where he sees the mysterious light and the odd creature, which has arms and legs, with a row of spikes running down its spine. Ted reaches safety, then goes to the lab, where he informs King that the fisherman had died from radiation burns, not natural causes. Ted asks for detailed charts of the ocean and King promises to bring them to his house that afternoon. Ted agrees, and there, King gives him the charts and reveals he knows that Ted is a scientist famous for his experiments on the biological effects of radiation on marine life. Relieved to be able to confide in King, Ted admits that he is investigating the nuclear light source and the monster, although King dismisses his concerns. Ted, who had conducted similar experiments on a much smaller scale, is worried that the light is man-made and can be transformed into a dangerous weapon. Ted theorizes that the monster gets sustenance from the light and warns that it and the light must be destroyed. King is affronted that Ted might suspect him, but Ted reveals that King is not under suspicion because its creator has offered to sell the technology to foreign governments. King is horrified by the news, but their conversation is interrupted by a call from Grant, who requests diving equipment for the following morning. Meanwhile, George meets with his former lover, Wanda, who is a secret agent for the foreign government seeking information about the nuclear light, which was indeed created by King, although for purely scientific reasons. Wanda warns George that he must stop Grant's dive and informs him that he has only two more days to provide the necessary intelligence. While George returns to the college to sabotage the diving gear, Grant meets with Ethel. The embittered Ethel reveals that her son died while collecting specimens for King, and Grant persuades her to obtain a wax impression of King's lab keys. Soon after, Ted is walking with Lois on the beach while a young couple go scuba diving in the cove. After they are killed by the phantom, their bodies are washed ashore, where Ted and Lois find them. Ted sends Lois to find Grant, after which George, who has been stalking Ted, shoots at him with a spear gun. George's shot misses its target, although George succeeds in escaping. At the morgue, as Ted and Grant discuss the corpses, Ted reveals that he is also working for the Department of Defense. In the morning, Ted and Grant are preparing for their dive when the poison George inserted into the gear almost knocks out Grant. Ted revives him and cleans the equipment, after which the men make their descent. They see the monster but manage to evade it and reach the surface safely. Meanwhile, at the college, Ethel notices that a spear gun is missing, and George threatens her again when she states that she saw him with it. George then finds Wanda, who reveals that Ethel met with Grant and orders George to "take care" of Ethel. Later that night, King discovers that Ethel has obtained keys to his lab and searched it. Ethel then goes to the beach to meet Grant, but George kills her with the spear gun before she can keep the rendezvous. The next day, Ted and Grant are discussing the case when the sheriff arrives and confirms that George killed Ethel and shot at Ted. Ted informs King, then urges him to provide the necessary information to destroy the light source and monster. King admits he activated a uranium deposit in the ocean floor in order to create the nuclear light but, unwilling to end his experiment, asks for an hour to consider his options. While Grant and the sheriff locate and arrest George and Wanda, Ted comforts Lois, who knows that something is deeply troubling her father. Determined to find her father, Lois insists on going to the lab, and Ted accompanies her. As they are walking along the beach, however, they see a large ship explode in the ocean, just as it passes over King's nuclear light. King also sees the explosion and, tormented by what he has wrought, destroys his laboratory. He then grabs a bundle of dynamite and rows out to the cove. King succeeds in planting the dynamite but is seized by the monster before he can escape, and they are both killed in the explosion, which covers up the light permanently. Grant, Ted and Lois watch the explosion from the beach, and Ted soberly comments that King has paid for his mistakes.