[WARNING: The following story contains spoilers from Sunday's episode of AMC's The Walking Dead. Read at your own risk.]

"They aren't all going to make it."

Rick's words to Michonne and Glenn in the early moments of Sunday's The Walking Dead were referring to the Alexandrians in their company. And although Rick was eventually proven correct, one of the people not making it was, sadly, one of the cast's key members. In other words, despite the episode being called "Thank You," there will likely be plenty of angry fans after this one.

But let's figure out how we got there. The episode picks up where Episode 1 ended, with Rick (Andrew Lincoln) & Co. running back toward Alexandria because of the sound of the horn. Naturally, most of the Alexandrians in the group are terrified — especially after the whiny Barnes gets eaten — but Rick has a plan. He's going to run back to the RV, swing around to cut off the back half of the herd and try to lure them back on course. In the meantime, Michonne (Danai Gurira) and Glenn (Steven Yeun) will lead Nicholas (Michael Traynor), Heath (Corey Hawkins), Scott (Kenric Green), Annie (Beth Keener), Sturgess (Jonathan Kleitman) and David (Jay Huguley) back to Alexandria.

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"If something's in front of you, you kill it. No hiding, no waiting. You keep going," Rick tells Michonne and Glenn, before adding the words above. "They aren't all going to make it. You try to save them. You try, but if they can't keep up, you keep going. You have to. You make sure you get back." Unfortunately, Heath overhears Rick's orders and spends much of the episode with his eye on Michonne, who he believes will cut bait and run at any minute. But both Michonne and Glenn agree that Rick's view of the world isn't exactly theirs. "I need to get home but I'm not leaving them behind," Glenn says.

And sure enough, things quickly go sideways. First Annie twists her ankle. Then, during a small skirmish with walkers, Sturgess freaks out and accidentally shoots Scott in the leg before running away like a coward. Making matters worse, David gets bitten on the shoulder. The group makes their way to a small town to find a place to rest and tend to their wounds. But Glenn has another idea: If he can burn a few of the buildings, the fire might distract the herd from heading on to Alexandria. Nicholas tells Glenn about a feed store nearby and agrees to lead him to it.

While they wait for the duo to return, Annie and Scott urge Heath and Michonne to leave them behind for the good of the group. Heath refuses, shooting some barbs at Michonne. When she asks him what's going on, he admits he overheard Rick's orders. And although she insists she and Glenn are going above and beyond the group, she also defends Rick's warped worldview. When Heath insists that he has encountered the world that Rick has during scouting runs, Michonne quickly counters. "Have you ever had to kill people because they killed your friends and were coming for you next?" she asks. "Have you ever done things that made you feel afraid of yourself afterward? Have you ever been covered in so much blood you didn't know if it was yours or walkers or your friends? Then you don't know."

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While Michonne and Heath debate the episode's major theme, Nicholas is haunted by it. While leading Glenn to the feed store, Nicholas sees a young walker he recognizes as one of his group that he left behind on one of his earlier runs. Glenn insists to Nicholas that he is no longer that cowardly person, and Nicholas, who seems to struggle with his courage multiple times throughout the episode, puts his former friend out of his misery. But things get tricky once they arrive at the feed store to learn it's already been burned down. And although they frantically search for another building, they've run out of time: The herd is there.

Realizing they can't wait any longer, Michonne leads her group out of their hiding spot and try to evade the herd. Annie's bad ankle gives out almost instantly and she becomes zombie dinner. They reach a gate, and Heath helps Scott over as the herd closes in. Although they claw at David and Michonne, it is David who eventually falls and is devoured while MIchonne makes it to safety. While she laments not being able to let David get home to tell his wife goodbye, Heath, finally realizing the validity of Rick's words, urges the group to move on.

Things are no better for Glenn and Nicholas, who find themselves trapped in a dead end as well. Although they find temporary safety atop a dumpster, Nicholas' old cowardice eventually kicks back in. Although Glenn can see him freaking out and tries to talk him out of daze, Nicholas instead puts his gun to his head, offers the episode's titular "thank you," to Glenn and pulls the trigger, spraying Glenn's face with his blood. As Nicholas falls, Glenn is taken down with him and the herd of walkers quickly descend on Glenn, ripping open his torso and munching on him. It's truly one of the hardest scenes to watch the show has depicted, as Glenn silently screams as his blood and entrails come pouring out. Thanks for nothing, Nicholas.

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Remarkably, the episode doesn't end there. Rick makes it to the RV and drives to where he thinks he'll be able to intercept the herd. However, he is quickly attacked by the wolves rebuffed by Morgan (Lennie James) last week. Rick dispatches of them, but the gunfire may have done some damage to the RV, because just as the herd closes in, Rick can't get the vehicle to start. Gulp.

While I don't think we'll be losing Rick any time soon, Glenn's death should have a huge impact. For starters, Maggie (Lauren Cohan) has already lost a father and sister. This blow could be too much. But more importantly, I fear what Glenn's death will do for the tone of the show. He's always been a heroic optimist. (In fact, you could argue his belief in Nicholas after all the things he's done wrong, was his fatal mistake.) And while I understand Rick's increasingly bleak worldview, I enjoy seeing the light that someone like Glenn could sometimes add. He could reason with Rick and make sense of even the worst situation. Without him, it seems only more doom and gloom is in store.

What do you think? Are you sad to see Glenn's death?

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