Five years after the Baizi successfully survived the surface invasion, the mountain gene crisis, the Ari intelligence crisis and the sky radiation crisis, the sky people and the surface people led by XiaooHeda returned to the ground. When rebuilding their homes, they accidentally discovered that the underwater intelligent base built by the US National Defense before the war had surfaced due to the termination of the backup power supply. After exploration, they found that there were no survivors in the base. After repairing the power supply equipment, the sky people entered the control system of the underwater base. It turned out that this was a space warfare base that had been developed during the Cold War. The reason why it was built on the seabed was for safety and confidentiality. The underwater base can access the military satellites that are still in operation. It was accidentally discovered that the United States had secretly contacted the Protoss civilization in the universe. The diplomatic fleet of the Protoss civilization had set out a hundred years ago and has now entered the edge of the Milky Way. The Protoss civilization discovered that the Earth civilization no longer exists. At the same time, Ari's system that was backed up in the space station at that time mistakenly determined the intention of the Protoss civilization and hoped that they could help humans rebuild their homes. However, the Protoss civilization has begun a plan to colonize the Earth. The mission of the diplomatic fleet is to eliminate the remaining civilization on Earth and establish a new order. How the sky people and the surface people will use the Earth's regressive civilization to defeat the universe Protoss will be the highlight of this season. The basic plot setting is that the Protoss civilization is also a carbon-based creature with a similar appearance to humans. Its weapons are also developed based on quantum mechanics, but they are more advanced than the technology of humans. After the Protoss civilization and the Earth civilization discovered each other, they believed that the technology of the Earth civilization was explosive and might not be able to maintain its technological lead after arriving on Earth. However, due to their curiosity about the unknown world, they sent a diplomatic fleet of 2 starships and 10,000 Protoss warriors.