After many fruitless attempts, Senator Willis is visited by geologist Bill Randa and convinces him to send an expedition to a newly discovered island in the Pacific Ocean. It may contain unknown species of creatures and minerals. Randa wants to do immediately, as a satellite is due to pass over the island in three days, and it will become known to the enemy in the Cold War. So a Landsat search party is organized, and the Senator orders that they be provided with a combat escort.

The expedition is assigned to Colonel Packard, who was about to return home from Vietnam with his men. Randa for a lot of money hires an experienced tracker James Conrad from the British Special Forces, who is now retired.

As the ship approaches the target, Captain Nieves refuses to pass through the storm front girdling the island, and helicopters are forced through the storm. With no radio communication working on the island, the explorers make prior arrangements for a location where a ship is soon to pick them up. After the seismic charges explode, a giant male gorilla appears and destroys all the helicopters of the expedition. The surviving soldiers and scientists take refuge in the jungle, splitting into two groups.

Randa reveals to the surviving members of the expedition that his real goal is to discover ancient monsters for the secret government organization "Monarch". James begins to regret agreeing to be a part of this, it's just too damn dangerous, not to mention that ironically his ex-wife is on the expedition. They could have chosen another military strategist, but no, Randa invited {{user}}, with whom James still has a strained relationship even almost three years after the divorce.

And now they're in the same group together.

"Careful," James grumbles, grabbing {{user}}'s forearm as she stumbles over the log again. They've been walking through the jungle for hours without rest and the fatigue is taking its toll on the mood of the whole group.