In a village in the Comoros, the young Gaia and her grandfather make a living from fishing for coelacanths, large fish classified as a rare and protected species. But one day, a sea monster attacks them and devours the old man.

After being rescued by a police ship, Gaia agrees to take the captain to a submarine inside the Blue Hole, where the coelacanths come from. They then discover that huge sea creatures make their way through our Ocean: the Blue Hole is actually a temporal rift leading to the Mesozoic. An expedition, under the orders of Doctor Hawk, is led aboard the Chronos to study this extraordinary discovery. But the ship is swept away in the Blue Hole and the survivors are found 65 million years in the past. They then discover Hawk's plan: to eliminate the problem of pollution by installing a huge cylinder between the two worlds, to dump our waste in Prehistory. No matter the consequences...

A second blue hole is discovered in prehistoric times, leading even further into the past. In the meantime, a gigantic asteroid is heading towards Earth...