Doctor steven and project X crew are exploring a cave they found on there radars that could see or detect any cave or object close to them, when they got there they found a small cave that had another entrance which was deeper and longer hole so they prepared to go inside the cave to explore the new minerals they may find in that cave they found.

 So when they got to the deepest point of the cave they called Marry who works with Project X which also is married to Dave and they have a daughter named Stef, so Dr. Steven calls marry because crew found painting on the wall and also legends that had been made long time ago then Marry saw the painting and the legends on the wall and since she was familiar with the writing and painting on the wall, she told Dr. Steven that before humans Colossal monsters ruled the world.

Then when they mentioned that everybody was shocked and confused so they when to the top of the cave to go and research about what they had discovered and saw down in the cave which they called it the Hollow Earth, and Marry and Dave were so scared and sad because this encounter made them remember about memories about other monsters, they had lost their small child on the hands of a monster but they thought those monster were the same which there were not the same. So they got back to the Project X lab they research the things they capture and saw  in the Hollow Earth then moments after they started the research Marry told Dr. Steven that what they saw in the Hollow Earth was events that is what happened when the monsters ruled the world and it was written by a tribe that lived in those time periods so what the writing on the wall were talking about was about the real colossal monsters which in one of the paintings it stated that one of those monsters was king leviathan which was the ruler until the second monster which in the painted they know him as Gojira which for the tribe they saw him if he was a god because he 

saved them from and also the tribe stated that if king leviathan woke up from the cave he was frozen on Gojira would be the only monster capable to defeat him.

So to avoid that Project X made a machine that they named Prototype X which took orca communicating voices so they could have a chance they could communicate with the monsters and try to get them in there side before anything bad happened.

But there was spies that were send by another group of corrupted army team that wanted to steal the machine so that he could have the power to control the titans to his own good, however it was not easy to find Project X base which was underwater so the corrupted soldiers got ready because there mission was to steal the prototype X which they were going to use to control the monsters for their own benefit so since they had spies on project X labs the spies implanted a usb that had a virus that disable all the cameras systems and so they could get the exact location of the place so once the corrupted soldiers had the location to go and steal prototype x they go armed man and once in the lab and started to shoot the place up until the got there hands in the prototype X they all left leaving marry and Dr. Steven because they went to hide in a vault. But after that also the soldiers got control of the iceberg where king leviathan was on, so they were trying to wake him up to control him and rule the world with his the team of the soldiers set up a big dose of highly explosives and started setting them up.

After they set up the bombs around the ice berg king leviathan was trapped in, the Capitan of the corrupted  soldiers gives the command to detonate the bombs then all of the ice starts braking from were king leviathan was trapped in, when he got out they tried using prototype X to control him, but king leviathan did not seem to care about that, so he just squished the Capitan with his enormous feet and b out of the chains he was on so he swim to city and there he started to attack Boston.