After her mother's death, Evie moved in with her aunt, who lives in the house where she spent her summer vacations as a child. When strange things start happening, like sudden growth spurts and unexpected strength, she can't understand what's happening to her. When she has a sudden and uncontrollable urge to protect Kitty from an unkown threat, it's revealed that she is actually a Shield, and Kitty is a Spark. An experiment generations before has led to a group of genetically modified superhumans, who become either Shields (protectors) or Strays (attackers) when they encounter the right person (Spark).
Evie now has the job of protecting Kitty from an unknown assailant, which would be difficult enough, but she's untrained, has no idea who she's looking out for, and has to go to a new high school where everyone's a potential suspect. As an added complication, she's had a crush on Kitty's twin brother, Jamie, forever and hasn't yet forgiven him for a humiliating incident a few years earlier. Now she has to spend much more time with him than she'd like, and he's setting off sparks of his own. Can Evie stop the killer before he gets to Kitty?
Spark is clever and thrilling and at one particular point left me gasping in shock. That doesn't happen very often, and I love it when it does.
Spark raises questions of genetic predetermination, free will, designer genes and all the ethical issues that go along with that.
I thoroughly enjoyed it and can't wait to get my hands on Stray. Seriously, go read this book now!