Maggie Greene lived with her father Hershel and her sister Beth in a secluded farmhouse. When Rick shows up on their porch one day with a gravely-injured Carl, Maggie is tasked with finding Lori to relate what's happened.
An expert equestrian, Maggie also uses horses to make trips into town for supplies. During one such run, Glenn tags along and she propositions him for sex — though afterwards she tells him it was a "one-time thing."
Despite Hershel's initial disapproval, Maggie pursues a relationship with Glenn and soon develops deep feelings for him. Maggie's opinionated nature shines through in that relationship as well, when she chafes at Glenn's willingness to put himself in harm's way. "You're a leader," she tells him, but he lets Rick and the others use him as "walker bait."
Maggie's compassion and her deep loyalty to loved ones prove to be her overriding concern. When the farmhouse is attacked and the group is scattered, Glenn soothes her by assuring that Hershel and Beth made it out alive.
After spending the winter on the run, the group spots an abandoned prison and Maggie proves herself a capable soldier in helping to clear the yard of walkers. However, Hershel's leg is bitten and amputated in the process and Maggie must come to terms with the possibility of losing her father. She sits with Hershel while he's unconscious and urges him to let go. "You don't have to fight any more," she sobs. "Thank you for everything."
Maggie is also present when Lori goes into labor during a walker attack on the prison. Once Lori realizes she's about to hemorrhage to death, she orders Maggie to cut her open. Maggie obliges, saving the baby but losing Lori in the process.
During a supply run, Maggie and Glenn are kidnapped by Merle and taken to Woodbury. The Governor psychologically tortures Maggie, forcing her to take off her shirt and threatening Glenn's life if she won't cooperate. When he puts a gun to Glenn's head, she finally gives up the location of their group.
Maggie and Glenn are eventually rescued, but back at the prison, Maggie withdraws as she tries to cope with the Governor's assault.
Making matters worse, Glenn pushes her to discuss the incident, causing a rift between the two. Glenn eventually apologizes for his behavior, and they make up. When he proposes marriage to her in the prison yard, she accepts with tears of joy.