Annie Martinez is the older sister of Rafael Martinez, and was Project Phoenix's first experiment. She is 19 years old, and a skin-walker. Her mother joined the experiment so that her children could be skin-walkers, not wanting them to feel the absence of the shifts. However, after the gene was reactivated in her children, Annie's mom took them and ran, along with the other mothers who took part in the experiment. Annie was interested in becoming a painter, having earned her mother's artistic side. She was a quite, shy girl, as described by her brother. When her mother died of cancer, Annie took responsibility for the family. She would work two jobs at a time to earn money for them. But after a few years of Shifting she started to regress. Annie stopped caring for things like painting, and would only want to sleep and eat. She began to be more animal-like, not being the protective sister that Rafe knew.It is known that this is a common side affect of the skin-walkers, affecting Maya as well.
When Annie moved to Salmon Creek with her brother, they lived in a cabin that they 'inherited'. She meets Samantha Russo when her brother reveals that he thinks she is the skin-walker their mother told them about. Sam is upset with Annie, who is obviously mentally challenged, and lashes out at her in annoyance. Rafe finds them and gets mad at Sam, acting cold towards her whenever they meet. Some time later, when Rafe suspects that Maya is in fact the skin-walker, Annie goes to meet her at the school too. Maya acts much nicer to her than Sam, and reveals to Rafe that she wanted to introduce her to the others in Salmon Creek. When Annie finds Rafe and Maya kissing in a tree she climbs up to talk to them. After she jumps down, Rafe tells her to be careful in case she makes Maya fall, but Annie just says that she would "land on her feet, just like me" referring to their feline ancestry.
Once she is captured by the Nasts, they help her to work through her regression,with her claiming that she got about "20 good minutes a day" with the medicine they were giving her. Annie gets to meet Maya 'herself' and tells her that she is happy that her brother has someone like her. Maya remarks that Annie is still the girl she met before, but more composed, her hugs still kind but not the fierce ones she greeted Maya with before. During the evacuation Annie suspects that Maya and her brother will be escaping in the van and asks the guards if she can switch with Hayley as she doesn't think she is meant to be with them in that van. When her brother tries to talk to her she assures him that she has a doctor in the other van who will be able to help her. Annie is later reunited with Rafael and they live together in a cabin in Badger Lake.
"This one was taller than me, with long black hair that curled over her faded denim jacket. Native or Latina. She was watching me and making no effort to hide it. Mina Lee's partner? If so, she needed lessons in subtlety even more than Mina did.
When I headed her way, she started grinning and rocking on her toes, like she was fighting an urge to run toward me. She looked about nineteen, but her grin belonged on the face of a five-year-old. She was bouncing like a five-year-old, too.
When I got a better look at her face--high cheekbones, sharp nose an chin, and slightly slanted amber eyes--I realized this had to be Rafe's older sister. I'd never seen her before. Few people in town had. She was supposed to be an artist. Shy and reclusive, Rafe had told everyone. One look at this girl, so eager to say hello she could barely stand still, and I knew that was a lie. Surprise, surprise."