On a volcanic island in the Mediterranean, Dr. Valerie Cammon [Polly Shannon] and her colleague, Dr. Kim [Philip Moon], go exploring a cave in search of ancient relics. As they map the ruins, a violent seaquake shatters their ship, leaving no survivors, and the re-awakened ancient Lernaean Hydra begins to stir in the surrounding chaos. The storm roils the sea, the island itself seems to vanish, and the immediate danger shifts from archaeological mystery to surviving a legendary monster that has risen from myth.
Two months later, Vincent Camden [Alex McArthur] and Dixie Camden [Jana Williams] are plotting a man-hunt for a group of cranky, powerful millionaires. Their Captain, Captain Sweet [Michael Shamus Wiles], unaware of the Hydra’s return, suggests the nearby island as a substitute destination for a deadly game. The stage is set for a grim confrontation between the hunted and the hunters, while a far greater threat lurks just beyond the horizon.
Four ex-convicts—Tim Nolan [George Stults], Gwen Russell [Dawn Olivieri], Bob Crick [James Wlcek], and Ronnie Kaplan [Texas Battle]—are marooned on the shore, each given a 24-hour head start to scramble for safety. The next day, the rich hunters arrive with a disturbing premise: they believe their targets bear responsibility for crimes mirroring the losses they have suffered in their own lives. Kaplan’s guilt centers on a drunk-driving crash, Crick’s on rape and murder, Gwen’s on hiring a hitman to kill her husband, and Nolan’s on a fatal twist in an abduction—though Nolan is selected only after a heart attack interrupts the plan. The encounter, however, draws the Hydra’s attention, and both groups find themselves suddenly prey rather than predator.
As the Hydra rips through the assemblies, several figures fall to the beast, and some fugitives meet a brutal end as well. Amid the ensuing chaos, Cammon reconnects with the surviving fugitives and guides Tim toward a legendary relic—the magical sword of Hercules. With Cammon distracting the Hydra, Tim seizes the weapon, stepping into a desperate role as the monster looms closer. But tragedy strikes: Cammon is torn apart and eaten before the sword can fully turn the tide. Tim fights valiantly, managing to sever several of the Hydra’s heads, yet the last head remains a lingering threat.
With Cammon dead, the remaining fugitives press on, the Hydra still in pursuit. Only Tim and Gwen remain, and they return to the ship, unaware that the Hydra has stalked them and now travels as a single-headed, snake-like creature that can slip into the belly of the vessel. Gwen attempts to call for help, but the microphone is damaged. Vincent Camden blindsides her and uses coercion to push Tim toward a grim choice. The Hydra strikes Camden from behind and devours Dixie, leaving Tim to face the final confrontation with the creature. Grasping the sword again, Tim delivers the decisive, lethal blow, ending the monster’s threat—at a terrible cost.
