Born to Fight is the second installment in the Born Trilogy by author Tara Brown. The novel follows the story of Emma, a nineteen-year-old young woman who, along with a group of friends she has gathered and turned into a makeshift family, faces grave dangers in a world that has essentially been destroyed by government forces. Led by Emma, the group is fighting to tear down breeding farms and other institutions and return the world to a civilized place.

The book opens with Emma trapped in a medical facility in the crumbling city of Spokane, where a doctor has kept her sedated as experiments are performed on her, including a pregnancy and abortion. A very weak Emma manages to escape and reunites with Anna, the sixteen-year-old girl who has become something of a sister to her, and with the help of an older man who was a friend of Emma's late father, they escape from Spokane and return to one of the remote camps where their other friends greet them.

However, Emma learns some disturbing facts. Lenny, the man she knew as her father, was actually her uncle. Her biological father, Michael, secretly impregnated Emma's mother through artificial insemination, using his own sperm, in the beginning of his continuing experimentation with human engineering. When Lenny learned what had happened, he and his parents took Emma and kept her away from Michael, living off the grid in a remote farmhouse and a cabin stocked with supplies, as Lenny was a survivalist. This information is very disturbing for Emma, but learning that she is a Gen baby explains why she heals so quickly and has superior strength and speed.

At the retreat, Emma is reunited with her pet wolf Leo, along with Will, the man with whom she is in love, and his brother Jake, with whom she also shares an attraction. Other members of her makeshift family include a young girl named Sarah and a teenager named Meg. Emma soon learns that the other members of the retreat no longer trust her because Marshall, one of the camp's leaders, learned she was a Gen baby and sold her out to the people who had held her captive. He told others that she was not trustworthy.

Emma and her "family" leave the retreat and go to her cabin, then Will, Emma, Jake and Anna leave the others there and go to the home of Bernie, a former CIA agent with contacts in one of the new cities that has been built. Their plan to destroy the city and kill Michael is delayed when Anna becomes infected with a plague that leads to madness, so they shift gears and sneak into Michael's lab to steal a cure for her. They administer the cure, but it is not completely effective, so they take her to the lab, where Bernie tries to protect her as Michael attempts to perform experiments on her.

Eventually, Bernie, Will, and Emma get Anna out of the facility and back to their group. When the book ends, Anna still appears to be sick while Emma and the others prepare to stage a raid on the city, leading the reader into the final book of the trilogy.