The plot of StarCraft II: Heart of the Swarm is as follows: In the distant future, Earth would face a threat from outer space. A type of alien creature called the "Swarm" has spread across Earth. They can use Earth's energy and living things to communicate and infect. In order to deal with this threat, humans joined forces to establish a space fleet called the "Heart of the Swarm" to explore outer space and destroy the swarms. The Heart of the Swarm fleet consisted of a hyperspace ship, a Golden Fleet, a Shadow Fleet, and a ground force. During the exploration of outer space, the fleet encountered many difficulties and challenges, including fierce battles with the Zergs, exploring new planets, and discovering new alien civilizations. In the end, the Heart of the Swarm fleet successfully destroyed the swarm and the threat on Earth was resolved. However, the members of the fleet realized that the threat from outer space had not disappeared. They began to think about how to better protect the ecological environment of Earth and outer space in the future while exploring new interstellar adventures. This was the storyline of StarCraft II's Heart of the Swarm.