THE SPARK by Stephen C. Curro

Katrina grew up in a frigid world ruled by a tyrant.  By day, she works as a mechanic.  At night, she becomes the Ace, the King's personal assassin. She's not proud of her job, but she's accepted that it's the way things are.  At least she has her boyfriend Dez and his little brother Uriah to light her life.

When Katrina is ordered to quash a rebel attack on the King's Command Center, she thinks it's just another job.  But as she uncovers the plot, she is shocked to learn that Dez may be involved with the dissidents.  Now Katrina must make an impossible choose—eliminate the one she loves, or defy the King she swore to serve.

The Spark is a sci-fi thriller about love, betrayal, and how the futures of others, even a whole civilization, can be determined through a single choice.