Source material has major pros and major cons. Pro: The network and producers already have well-researched sets of storylines that just need to be adapted to fit a TV audience. Con: Readers know what to expect, and spoilers are everywhere. Now, Walking Dead fans are blindly treading into the future regardless of how many comic books they've read. Glenn is killed later in the series after a brutal beaten from the yet-to-be-introduced Negan. It's a moment that readers have anticipated for a long, long time, but if Glenn stays dead, it obviously can't play out in the same way. This could mean that the scene will go ahead, but the victim will remain a complete mystery until it's aired. That's exciting and terrifying in equal measures. Episode 3's bombshell is already causing huge ripples across the story.