Much like Game of Thrones, The Walking Dead has a huge amount of source material from which to draw. Unlike Game of Thrones, The Walking Dead comics are actually ahead of the show. That means that comic readers can occasionally get the drop on viewers. The two narratives are far from the same, though the comic did also kill Glenn during the group's initial meeting with Negan.
So what's next, according to the comic books? All out war. More specifically, the infamous "All Out War" arc.
Here's what happens: In the comics, Maggie accuses Rick of being responsible for getting Glenn killed, and Carl has to pull a gun on her to calm her down. They return to Alexandria to find that the others have captured Dwight. Rather than torture him, Rick turns him loose and tells Eugene not to manufacture bullets. Rick sends Jesus to track Dwight. Negan shows up to camp and makes Rick hold his bat, Lucille, while he struts around.
Meanwhile, Jesus is captured (on purpose) and takes note of the route to the Saviors' camp. Carl stows away in Negan's truck and kills two of his men before Negan overpowers him. In a classic villain move, Negan starts randomly revealing secrets to the person most likely to hurt him with them. Once Rick finds out about Carl, and Jesus returns to camp, Rick and the Rickettes set out to rescue the boy. Negan's troupe meets them in the road, and Rick and Negan fight. Negan turns over Carl out of respect (and because the plot demands he does).
That's when the Kingdom, and Ezekiel and his tiger come into play. We'll leave the rest a mystery, though you can read more about it here.
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