During Prehistory, this Gigantic Octopus was frozen in an iceberg during a fight against Mega Shark. In Present days, some whales accidentally release the two monsters by breaking the iceberg and they both rampage across the Pacific.
Giant Octopus starts by attacking a Japanese drilling platform. Later, he destroys a small plane sent to examine him. He is attacked by militaries afterwards, but he manages to escape from them.
Finally, some scientists succeed to lure the two prehistoric monster at the same place by using pheromones. They continue their fight and apparently both kill each other.