A man shoots a bullet into the head of a corpse wrapped in a sheet and instructs an unseen person, "The boat can leave now. Tell the crew." A few days later, an apparently abandoned sailboat drifts into the New York harbor, prompting two harbor patrol officers to investigate. Upon boarding, they discover a mess and soon encounter a grotesque zombie (Captain Haggerty) that viciously attacks them, killing one officer and being shot overboard by the other.
Assigned to cover the case is local reporter Peter West, who meets with Anne, the daughter of the boat’s missing owner. Anne reveals that her father has been missing for three months since traveling to the Antilles. Meanwhile, at the morgue, a pathologist and his assistant are shocked when the body of the dead officer begins to stir.
The next day, Peter and Anne travel to the Dominican Republic, where they encounter an American couple, Brian Hull and Susan Barrett, gearing up for a sailing tour in the Caribbean. They request to join them to reach the island of Matul, where Anne's father was last heard from. Despite warnings from the fearful locals about Matul, the four set off together.
On the island, tensions rise between Richard Johnson and his anxious wife Paola, as she insists on leaving due to reports of zombie sightings. Despite her fears, he remains to conduct research, ignoring the pleas of his superstitious assistant Lucas, who warns of rising undead.
A scuba diving trip turns deadly for Susan when she encounters both a shark and an unusual aquatic zombie. Meanwhile, Paola finds herself alone in their house. As she tries to cool off in the shower, she hears a noise and is violently attacked by a zombie, meeting a gruesome end when her head is impaled.
The following morning, Anne and the others reach Matul only to discover their boat has been damaged from the shark attack. They send distress signals that are answered by Menard, who reveals that more locals are mysteriously dying and returning as zombies. He also shares the tragic news that Anne's father had died months prior due to the same disease. Despite their disbelief, they listen to Menard talk about how the voodoo curses of a witch doctor are believed to be behind the epidemic.
Later, the group ventures to the Menard home, only to find a horrific scene: Mrs. Menard’s corpse is half-eaten, surrounded by zombies. Quick to react, they fight their way back to the safety of the hospital. Their escape, however, is fraught with danger as the undead are everywhere.
While resting, they unknowingly intrude upon an old cemetery, where the graves of long-dead conquistadors open up. Both Peter and Anne struggle to break free from the grasp of the resurrected corpses, but Susan isn’t as fortunate. Before they can escape, she’s brutally attacked and killed by a zombie, and the survivors are forced to retreat.
As night falls, they finally return to the hospital, where chaos reigns as the undead threaten from both outside and within. They begin barricading themselves against the onslaught, but tragedy strikes as one by one, their allies fall victim to the hungry zombies.
As the hospital succumbs to flames and chaos, Anne, Peter, and Brian escape, but their freedom comes with a devastating price. Brian is bitten and, as they manage to reach a makeshift boat, the horror of the situation escalates when they realize that the zombie epidemic has reached New York City.
With a looming sense of dread, Peter and Anne listen helplessly as news reports spread about the chaos in their city, unaware of the horrifying fate that awaits them with the reanimated corpse of Brian trapped below deck, desperate to get out. As dawn rises, a hoard of newly dead zombies marches across the Brooklyn Bridge, signaling that the nightmare has only just begun.
