Port Sinister

When explorer Tony Ferris receives money from a Florida marine institute to lead a Caribbean expedition to Port Royal, a sunken seventeenth century city, institute scientist Dr. Joan Hunter is dismayed. Although she doubts Tony's theory that the infamous pirate capital will reemerge briefly during an upcoming volcanic eruption, Joan agrees to be the expedition's "scientific historian." The night before sailing, Tony's maps and papers are stolen from his hotel room, and he is knocked out. Unknown to Tony, his attacker is boatswain John Kolvak, who is conspiring with other members of the ship's crew to take over the expedition and claim any treasure found on Port Royal. The next morning, Tony wakens in a hospital in South Carolina, where Kolvac had dumped him, still unconscious. At the same time, in Florida, Kolvac, first mate George Burt and radio operator Nick stage an accident while loading the expedition's schooner, the Neptune , which incapacitates the captain. Soon after, Joan shows up, and Kolvac informs her that he has the proper papers to assume captainship. Joan agrees to sail, even though Tony has not yet arrived. Before final boarding, however, Collins, a sailing acquaintance, blackmails Kolvac into adding him to the crew by threatening to expose Kolvac's devious past. Meanwhile, in South Carolina, Tony sneaks out of the hospital but cannot reach the schooner before it sails and cannot hail it because Kolvac has disabled the ship's radio. With a hurricane raging in the area, the Coast Guard refuses to deliver Tony to the Neptune , but he gets a tip to contact Jim Gerry, an alcoholic, daredevil pilot. Desperate, Tony hires Jim to fly him to the Neptune , and the two head out in the midst of the hurricane. Before catching up to the schooner, the plane runs out of gas and starts to drift. Using their parachutes as sails, Tony and Jim speed the plane toward the spot where Tony has predicted Port Royal will reemerge. The Neptune has already reached the site, and the crew watches in amazement as an underwater volcanic eruption forces part of the sunken city to burst out of the sea. Kolvac and the crew eagerly row to the new island and break into two groups to scour for Spanish Main treasure. As Kolvac and Collins search the remains of the governor's palace, Christie, the third member of their group, keeps guard outside. Just after Kolvac and Collins discover the palace's "treasure room," Christie is killed by a giant crab. On the Neptune , meanwhile, Joan breaks out of the cabin in which Kolvac had imprisoned her and swims to Port Royal. Upon reaching shore, Joan encounters the giant crab and screams, alerting Kolvac and Collins, who are about to cart off some treasure. The men tie up Joan and leave her to be devoured by the crab, but Tony and Jim show up in time to save her and destroy the beast. While Joan, Jim and Tony hunt for gas for the plane, Kolvac and Collins return to the palace for more treasure and discover Joan gone. When they spot Jim's plane nearby, they decide to fly out by themselves and go back to the Neptune for gas. Meanwhile, to give Jim and Tony enough time to sneak onboard the Neptune , Joan attracts the attention of Nick, Burt and fellow sailors Hollis and Akers, who chase her across the rough terrain. Jim and Tony obtain the gas, but upon returning to the plane, realize that someone has been there. After Jim fixes the plane so that only he can fly it, he and Tony return for Joan and are fired on by Nick and his men. While Joan, who has become trapped in a narrow, craggy passageway, struggles to free herself, Jim pretends he has been shot and Tony surrenders to the sailors. Tony and Jim then take their attackers by surprise and flee with Joan. In the treasure room, meanwhile, Collins pulls a gun on Kolvac, determined to keep all the loot for himself. Burt, however, sneaks up on Collins and shoots him, but Kolvac then shoots Burt. As the island starts to break up, Jim, Joan and Tony race for the plane, pursued by Nick, Hollis and Akers. Along the way, they encounter an area covered by a thin crust of lava, with quicksand underneath. Jim, Joan and Tony cross safely, but the sailors drown in the quicksand. Kolvac reaches the plane at the same time as Tony and the others, but because he refuses to leave the treasure behind, he is drowned in lava. Tony, Jim and Joan then take off as the remains of Port Royal descend to the sea floor once again.