On the eve of the United States Independence Day celebration, harbor police officer Nico (played by Michael Reilly Burke), who is distrusted by his superiors due to a false accusation case, and his soon-to-be transferred partner Walter are ordered to investigate the murder of a Russian tourist at the East River port in New York City. After seeking witness testimonies, they obtain information that the two victims were pulled into the river by a giant octopus. Meanwhile, ships on the East River catch fire and explode for no apparent reason, leading to multiple deaths, and rumors of an 'East River Killer' begin to spread. During a diving investigation, they encounter the giant octopus described by witnesses. Despite their struggle to fight back, Walter unfortunately ends up being swallowed by the octopus. When Nico reports the incident to his superiors, he does not receive their trust and is instead ordered to cease the investigation. Nico finds himself in a difficult situation, haunted by dreams of the octopus causing a catastrophic disaster during the Independence Day celebration. In a relentless effort to safeguard the citizens, he ultimately gains the assistance of Rachel (portrayed by Meredith Morton), the mayor's secretary. As Independence Day celebration night arrives, beneath the fireworks rising over the East River lies a lurking danger, while 12 foreign children participating in the celebration, led by Rachel, find themselves trapped in a tunnel that has been destroyed by the octopus...