On The Walking Dead, Morgan (Lennie James) and Carol (Melissa McBride) have been at odds since they met at the beginning of Season 6. The two characters' arcs have become entwined, as each represents a different way of dealing with the post-apocalyptic world. For most of their relationship, they've clashed over diametrically opposed ideologies: Morgan is as close to a pacifist as one can be in a world overrun with zombies, while Carol until recently espoused a mercenary kill-or-be-killed mentality. But now, at the start of Season 7, they've been forced together with their roles flipped. Their story in Season 7 will have to find them coming to some sort of understanding.

They met for the first time in the Season 6 premiere "First Time Again." Morgan had recently rejoined Rick (Andrew Lincoln) after his time literally in the wilderness. Morgan had a mental break after his zombified wife killed his son, and he wandered around slaughtering walkers and survivors in a bloodthirsty daze until he met Eastman (John Carroll Lynch), a Zen master who helped him recover. Eastman taught him the non-lethal martial art aikido and impressed upon him the idea that all life is precious. After Eastman's death, Morgan set out to find Rick to share his peaceful message with the violent leader.

Melissa McBride and Lennie James, <em>The Walking Dead</em>Melissa McBride and Lennie James, The Walking Dead

Carol had an almost opposite journey. The apocalypse transformed her from a submissive, abused housewife into a hardened killer. She has killed dozens of people to ensure the survival of her and the group, including the time she shot a child in the back of the head. She doesn't relish the killing, and each murder takes a psychological toll on her, but she does what she believes she has to do. She was formerly a devout Christian, but she lost her faith because she can't fathom why God — if he was real — would let this happen.

Morgan and Carol began to clash in the next episode when the Wolves attacked Alexandria and she fought back with extreme prejudice. She saved Morgan from getting chopped by an ax-wielding Wolf by stabbing the Wolf in the gut, which made Morgan mad, since he wanted to stop his assailant using non-lethal means. They laid out their different ways of seeing the world in that moment, in very simple terms:

"We don't have to kill people," Morgan said sternly, to which Carol replied with a dismissive "of course we do."

"Carol," he said, trying to get through to her. "You don't like it."

She tells Morgan to leave Father Gabriel (Seth Gilliam) to die at the hands of a Wolf, since he's not part of her core group and saving him would compromise their mission, but Morgan saves him anyway.

It's after the fight with the Wolves that all the killing really starts to weigh on Carol, and she starts to show signs of doubting herself. She and Morgan cross paths in the road as they're surveying the damage, and pass without speaking. At that moment, though, Morgan had a secret: He captured the Alpha Wolf (Benedict Samuel) and was going to try to show him the error of his ways.

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In the episode "Here's Not Here," Morgan tells the Wolf the story of how he became the peaceful, staff-wielding warrior he is now, but the Wolf seems unimpressed. Carol finds out that Morgan is keeping the Wolf in his house and having Denise (Merritt Wever) treat his wound. Carol tries to kill the Wolf, but Morgan won't let her. In the commotion, the Wolf escapes and takes Denise hostage. Morgan apologizes for hurting her, and Carol says she should have killed Morgan when she had the chance. Meanwhile, the Alpha Wolf saves Denise's life during the zombie swarm of Alexandria even though he doesn't have to and gets bit in the process, and then Carol shoots him, since she doesn't know at that moment he's had an apparent change of heart. But she hears him telling Denise to save herself, and she realizes that she and the Wolf were on the same side.

In the months after the swarm, all the killing finally breaks Carol. She starts smoking, and she starts carrying a rosary again. Later, when the gang attacks a Savior stronghold, Carol refuses to participate in the slaughter and stays behind to guard the perimeter with pregnant Maggie (Lauren Cohan), but they get captured by surviving Saviors. The leader of this group of Saviors, Paula (Alicia Witt), is a dark mirror version of Carol, and Carol sees what she could become if she fully gives in to fatalism. Carol and Maggie kill their captors and a group of Saviors Paula called as backup. Carol admits that she's not alright and can't keep doing this, and a few days later leaves Alexandria under the cover of darkness, leaving a note that says if she has to kill to protect the people she loves then she can't love them, because she can no longer kill.

Morgan and Rick set out after her, but Morgan sends Rick back to Alexandria because he's concerned Rick will kill somebody who doesn't need killing. He finds Carol and patches her up, but she runs away again. She's caught by a Savior who shoots her in the arm and leg, but Morgan arrives and shoots the Savior. Morgan broke his vow to not kill to save Carol, who has lost her will to kill.

This is where we'll pick up in the next episode, "The Well." Morgan and Carol are together in the Kingdom, having been rescued and brought there. Their places from where they were at the start of the sixth season have flipped — Morgan is grappling with the apparent reality that sometimes he'll have to kill, while Carol would prefer to be nonviolent. This is The Walking Dead, and Carol is wrong, just as Morgan was wrong: killing is necessary. So they both will continue to have to kill, and neither of them will like it, but perhaps they can put their heads together and come up with some rules for when killing is justified and when it's not.

The Walking Dead airs Sunday nights at 9/8c on AMC.