Major Byrne

In Inclement Weather, she is seen at the beginning of the episode when a member of the Ark says they saw movement in the woods and opened fire. When Marcus Kane grabs the gun from the man, Byrne admits she was the one that gave him the gun.

In Reapercussions, she is seen telling the Chancellor that he needs to take certain actions to maintain order in Camp Jaha. This leads to Kane enforcing a public whipping for Abby, as she helped the kids escape.

In Many Happy Returns, she shoots down Wick and Raven's beacon balloon, because the grounders can use it to learn their location. After she shoots it down she orders all guards to the fence line and to shoot any grounders they see coming from the woods.

In Human Trials, she has her men drag Clarke Griffin into camp asking how many of their people are out there, thinking she is a grounder. After Abby reveals it's Clarke she lets Abby treat her. She asks if Clarke is okay and apologizes for her treatment of her. She then asks where she has been and Clarke tells her, Abby and Jackson that she was at Mount Weather being held by the Mountain Men before Abby sends her away. In the meeting room, she advises caution when dealing with the Mountain Men since they know virtually nothing about them. When she asks about Finn and Murphy, Abby says to leaves them.

In Fog of War, she advises against a mission for the Delinquints to destroy Mount Weather's tower, but is overruled by Abby, who accompanies them with a select few guards.

In Long Into an Abyss, she is seen entering the meeting room, where she finds Abby, Jaha, Finn and Clarke talking about leaving or staying at Camp Jaha. When Thelonious orders Byrne and Sgt. David Miller to arrest Abby, they refuse. When Abby orders them to take away Thelonious, they go by her orders and arrest him immediately.

In Spacewalker, she is seen among the Arkers gathered around Clarke as she gives the terms for a truce between the grounders and Arkers: Surrender Finn for murdering 18 grounders. She later pulls Raven off a man advocating for this deal and Raven accidentally punches her in the face. Later, when Abby tells the Grounders they can't take Finn, Major Byrne stands armed ready with the other guardsmen in anticipation of a Grounder attack, but is stunned to witness Kane return to Camp Jaha.

In Survival of the Fittest, she is seen among the grounders and Clarke Griffin, who are discussing a way to enter Mount Weather. However, when tensions rise during an argument over the death of a grounder's brother, Clarke storms out of the room, with Byrne chasing after her. Byrne, however, was attacked by a giant ape. When she finally finds Clarke, Byrne's right arm had already been severed by the beast. In her final words, she tells Clarke to "Save yourself", as she collapses to the ground.