Trista was born and grew up in Ann Arbor, MI until she was 15 years old. At the end of her freshman year of high school, she ran afoul of an underworld deal and, in defending herself and trying to get away, killed two men and critically injured a third. That third man was an undercover FBI agent, and Tris's involvement in the bust immediately garnered the attention of the US Clandestine Services. She was recruited, not entirely of her own accord, and shipped overseas to complete her training.
Tris is an incredible field agent- an excellent spy and an even better assassin- with all the skills that a solo operator would need and the capacity to learn more quickly, thoroughly, and well. Her superhuman memory coupled with her imagination and physical skills make her one of the best agents in the business.
Now, if only she knew who the good guys were...