Tyreese, Mika and Judith (AMC). Tyreese, Mika and Judith (AMC).

It’s been a while since we’ve truly visited the human darkness that exists in “The Walking Dead.” Sure, the show is about survival — and for much of the second half, it has been focused on how a once solid group, now splintered, can survive in the wilderness. So far, the danger has been more about the walker that might be outside the front door, not the person who’s already inside the house.

This episode reverses that trend.

From the beginning, we get a hint of what is to come. Carol warns Tyreese that Mika and Lizzie are a handful, both in their own unique way. Lizzie has a misconstrued perception of the walkers, while Mika “doesn’t have a mean bone in her body.” Carol said that as a way of comparing Mika to her own daughter, Sophia. Essentially, the girls are not the best traveling companions. They are emotionally strained — and this is coming from Carol, who is still hiding her murderous past from Tyreese.

The group of five  — Tyreese, Carol, Lizzie, Mika and Judith — takes a break from the journey to Terminus (the Sanctuary) after discovering a cluster of houses. There’s an ominous cloud of smoke from a fire in the distance (the house that Daryl and Beth torched last episode?) but that doesn’t deter the group from picking pecans from a tree and setting up camp inside one of the houses. They seem happy at first. Tyreese, still blissfully unaware of Carol’s actions, tells her that he trusts her and that they should consider staying.

But if there is anyone to distrust, it’s Lizzie. She is deadpan and limp when a zombie attacks her, watching as Mika is the one to draw her gun and shoot. She breaks down in agony when Carol stabs a walker she claims to be playing “tag” with in the home’s front yard. She is caught by her sister feeding mice to the walkers, telling Mika she “can get you all to understand it.”

Lizzie finally cracks in the most twisted, gut-wrenching way. Carol and Tyreese come back from a hunting trip to find that Lizzie’s killed her own sister, bloody knife in hand. Lizzie tells them she didn’t touch the brain; she simply doesn’t understand that when Mika comes back she won’t be Mika anymore.

The act was shocking, and so was the act that followed. Carol’s decision to kill Lizzie — using same rationalization that allowed her to kill Karen — was a reminder of just how brutal “The Walking Dead” can be. She walks slowly with Lizzie out to the grove, tells Lizzie to “look at the flowers,” aims her gun and shoots.

Carol’s inner demons  are really laid bare here. She is someone who believes walkers are not the only threat to survival, and that her choices are made for the greater good. She also recognizes how dark and troubled she has become herself, and goes so far as to tell Tyreese at the end of the episode that she was the one who killed Karen. She expects Tyreese to kill her — and even hands him the gun to make it easy — but instead finds forgiveness.

“It happened,” Tyreese says. “You did it. It’s a part of you now. Me too. But I forgive you.”

Unanswered questions: This episode so neatly wrapped up so many past unanswered questions (Lizzie was feeding mice to the walkers at the prison) that there is little left unanswered. We can only look to the future. Will Carol ever really come to terms with what she’s had to do, and what she’s witnessed? Will the trio (sans Lizzie and Mika) make it to Terminus?

Romance report: Nothing for this episode.

Past ‘The Walking Dead’ recaps:

‘The Walking Dead’ recap: Peach schnapps, or moonshine?
‘The Walking Dead’ recap: Saving humanity
‘The Walking Dead’ recap: Following the scattered survivors