Olesya is an agent with an unnamed agency.
I do not know if those that she works with would even qualify as an organization; it seems to me more of a group of determined individuals with a single purpose in mind. That purpose is the destruciton of a vast international cabal known as the Fifth Column (FC). To grasp the reach and the power that the FC has is enough to unnerve the staunchest opponent. As we are told in a blurb, the FC is "the world's most powerful and secretive organization. They run our militaries. They run our governments. They run our terrorist cells." Who exactly is the 'our' here? Apparently everyone. Russia, China, the US, the UK, you name it, the FC has their iron grip on the hands that wield any power. And they are constantly looking for better ways to first maintain and then expand that frightening grip.
The adventures of which Olesya is the starring player is really a continuation of the series of stories. While that set of capers might be named for the organizaiton in question, it dealt with the actions of a trio of former FC operatives turned into resistance fighters: Sophia, Damien, and Jay. These three had dedicated their lives to bringing down the FC.
The stories told in this second collection deal with a different set of resistance-oriented operatives spearheaded (IMHO) by Olesya; this second set is primarily Russian in origin. We will soon run into that first group and they will become intimately connected to Olesya and those told in these Helix adventures.
The name Helix is very important to these stories because of the now famous double helix of DNA, the blueprint and building block that make up each of us (and all living things). Some time before the stories begin, the FC under the cover of a well-respected scientific program to map the Human Genome started being able to recognize extremely exceptional young people from around the world. The potentially best of the best of the best are offered scholarships to a prestigious school. That school would, however, turn out to be a rigidly run training facility for future operative assassins working for the FC. Those who survived the intensive training would go on to have careers serving the masters of the FC; those that fell short would not be allowed to rise again.
Olesya is one of those that succeeded and became a near legendary operative. Over time, though, she began to realize what she was working for and eventually decided to not only make a break from it, she began to try to destroy it.