Unseen Servant

Was it an accident, or an assassination? 

"There is an unseen servant, one that plotted against your president, one that wanted your father to die. One that could go places and open doors without notice." 

US Air Force Captain Lani Knight is an agent in the National Security Agency. Her older brother, Adam Knight, is a Secret Service agent, assigned to the President's detail. They are mutants, part of the 5% of the world's population with a 24th chromosome that gives them special abilities. 

Five years ago, their father was killed in an accident, an explosion that also killed President Holly Taylor. Now, they have learned information that implies that it may have not been accidental, and not just another Presidential assassination. 

Lani and Adam must work alongside mutants and humans to learn the truth about their father and his death from people who do not want the past revisited.