FBI veteran undercover agent Art Jeffries was dismissed from a battle due to a conflict with the captain of the operation during an investigation into the bank robbery case, and was sent to a plain job. However, one day, the FBI gives him instructions. It was about the whereabouts of Simon, a 9-year-old child whose parents were assassinated. Simon, an autistic child with a great ability to solve puzzles, discovered at a glance the code of "Mercury", a system developed by the National Security Agency NSA for $2 billion.