Sunstorm opens with the last chapter of Time's Eye as its initial chapter, and Bisesa Dutt is in London, reunited with her daughter. It is June 9, 2037, the day after her helicopter was shot down in the North Western Frontier Province of Pakistan. The five years that she spent on Mir, an alternate Earth, are now only memories (though the fact that her body has aged five years since June 8, 2037, will eventually serve as some confirmation of her story).
In the meantime, a major solar event occurs on June 9, disrupting virtually all of the Earth's electronic hardware. Dramatic as it is, this phenomenon is only a minor precursor of a far more massive solar eruption about five years off. Scientific models of the projected 2042 event make clear that the Earth will be sterilized completely by the upcoming solar burst. The effects will be so powerful as to even endanger astronauts on Mars.
Rather than sit by and allow the sun to just destroy all of earth's life, political leaders (most notably the President of the Eurasian Union, Miriam Grec), and scientific leaders (led by Siobhan McGorran, the Astronomer Royal) decide to embark upon an ambitious plan to literally shield Earth from the worst effects of the storm. The plot is further complicated when information from Bisesa's odyssey makes it clear that what is happening to the sun is not simply a random happening in nature, but is rather the result of events set in motion by an alien intelligence, known as the Firstborn, since they were the first alien race to reach sentience, and thus the most advanced civilization in existence in the universe. They are determined to stop mankind from infiltrating the stars, since they believe mankind to be a disorderly and wasteful life form, increasing entropy with its energy usage and eventual wars, thus hastening the Universe's eventual heat death.