Jemeka Adams, a military veteran, is in town to meet Raven, a mutual friend, to help celebrate their best friend Emerald's birthday. Raven tells Jemeka that Emerald is in the hospital because Emerald tried to commit suicide. Jemeka races to the hospital to find out Emerald succumbed to her injuries. Devastated, Jemeka attends the funeral, confused as to why Emerald would kill herself. Raven tells her that Emerald was brutally assaulted during her last deployment by the same people, known as the Pack, who assaulted Jemeka on her last deployment. Raven tells Jemeka that Emerald tried to forget about the situation and was overcome with shame and grief, causing her to take her own life. Jemeka vows to go after the Pack and Raven reveals she works for an organization that that avenges people who are victims of domestic abuse, assault, and other egregious acts. Jemeka trains, passes her evaluations, and initiates into the organization. She is given a code name, Onyx, and her first assignment, which is to take down the Pack one by one. As Onyx goes deeper into her assignments, secrets are revealed about everyone, including those close to her.