During the search for Eugene, it becomes painfully clear that a new threat has arrived.
Alcohol-Induced Idiocy: The Hilltop teens get drunk and play a form of horseshoes with a walker in a pit. Henry stays sober and alert enough to kill the walker before anything bad can happen.
Arbitrary Skepticism: Discussed when Eugene hypothesizes that the walkers are somehow evolving. Daryl and Aaron say it’s a ridiculous notion, but Eugene and Jesus point out that the undead are already a ridiculous notion.
Book Ends: Jesus’ debut served to introduce the Saviors as the next major antagonists of the series. Jesus’ death serves to introduce the Whisperers as the next major antagonists of the series.
The Bus Came Back: Earl makes his first appearance since the second episode of the season. Alden also returns for the first time since the second Time Skip.
Call-Back: Earl admits that he knows where Henry is coming from regarding his drinking binge, and mentions his incarceration for his actions in the season premiere.
Character Death: Jesus is taken off-guard and killed by a Whisperer.
The discussion on the concept of evolving walkers hits a few of the same beats as the Arbitrary Skepticism-laden discussion about the chupacabra in Season 2’s “Chupacabra” (in which Daryl said that the idea of chupacabras being real isn’t any stranger than the undead).
In Season 3's "Clear", Morgan ranted about "people wearing dead people's faces". At the time of the episode's airing, the Whisperers had not made their comic debut, making it into a sort of meta-foreshadowing. As of this episode, this foreshadowing has come to pass.
Season 4’s “Alone” featured Maggie, Bob, and Sasha facing off against a herd of walkers in a foggy cemetery, much like the climax of this episode.
The Hilltop kids recklessly playing with the walker, which disgusts the more experienced Henry, hearkens back to Aiden and Nicholas’ similar actions back in Season 5’s “Remember”.
Cryptic Background Reference: More hints as to the big thing that went down during the Time Skip. It involved Michonne making some difficult choice that kept the communities safe, but led to their estrangement.
Death by Adaptation: Jesus is still alive and well in the comics as of this episode’s airing and ended up surviving the entirety of the comic's run. In the comics there wasn’t a six-year Time Skip, meaning Jesus in the TV show did survive past the point his comic counterpart has, even if the Whisperer arc as a result of the Time Skip didn’t happen until later in the timeline.
Didn't See That Coming: After years fighting them, being fatally stabbed by a supposed 'walker' was clearly just about the last thing Jesus was expecting. He dies with a look of utter astonishment on his face.
Green-Eyed Monster: Henry is jealous that Enid has formed a relationship with Alden, and has to blow off some steam.
The Guards Must Be Crazy: Gabriel and the other guards at Alexandria fail to remember to lock Negan’s cell.
Hope Spot: Jesus manages to take down all but two of the walkers between him, the others, and certain escape. He kills the first one with ease... and then the second one dodges his attack and stabs him.
In the Back: The Whisperer fatally stabs Jesus this way.
It Can Think: Daryl, Aaron, Jesus, and Eugene spend the episode questioning why the walkers are behaving so unnaturally (they’re idly wandering in circles, they’re expanding their ranks at fast rates, and they’re ignoring sounds used to distract them), and wonder if they’re somehow evolving into more dangerous threats. Jesus worries that if they’re communicating with each other, they can learn to strategize and hunt. Ultimately Subverted, as the Whisperers are properly introduced as humans wearing walker skins.
Last Stand: Jesus ends up going out this way, though tragically, he has no idea the walkers he was facing off with could fight back.
The Load: Poor Eugene can’t contribute much to Daryl, Jesus, and Aaron’s rescue attempt due to his dislocated knee. He is able to kill one walker and eventually helps get the gate open.
Nobody Poops: Averted. Gabriel has to clean out Negan’s bedpan.
O.O.C. Is Serious Business: When the normally calm, forgiving Gabriel begins angrily ranting at Negan, the former tyrant realizes something is up and asks him what’s wrong, dropping his verbal abuse.
Outside-Context Problem: Daryl, Eugene, Aaron, and Jesus know the walkers are acting strange, and theorize they could be evolving. They do not learn until it's too late that it is in fact another group wearing the faces of walkers to blend in with them, as one of them is able to catch him off guard after he proves capable of dodging Jesus's attack.
Pet the Dog: When he learns that Gabriel is prevented from going to see his injured girlfriend due to his duty to guard him, Negan sincerely apologizes.
Sacrificial Lion: Jesus’ death serves as a bloody introduction to the Whisperers.
A Storm Is Coming: Daryl says this almost word for word as he, Jesus, Aaron, and Dog prepare to leave the field and continue their search for Eugene. In-Universe, it’s referring to an actual storm brewing. Out of universe, it’s Foreshadowing the horrors to come...
Tempting Fate: Earl promises Henry that he will put in a good word for him when Jesus gets back to Hilltop. Jesus is ultimately killed before he can return. Jesus' last words promising that he can handle the herd ultimately ends up sealing his doom as well.
Too Dumb to Live: The two Hilltop boys have lived most of their life behind Hilltop’s walls and don’t see anything wrong with sneaking out to drink and party at night in the woods. They also play with a trapped walker up close and personal.
Wake-Up Call Boss: The Whisperer that kills Jesus serves as this for the show going forward. After a decade of growing relatively comfortable dealing with walkers, from lone roamers to massive herds, the Whisperer serves as a startling revelation that the threats the survivors face are evolving and will require adaptation and changes in strategy from the survivors if they are to survive. The most martially capable survivor in the communities was easily felled when he was simply caught off guard on what he thought was a routine walker-killing spree.
We Have Become Complacent: Both Alexandria and Hilltop display some degree of this after spending the last seven years thriving peacefully. The Alexandrians fail to make sure a dangerous war criminal's cell is locked, and Hilltop has been unaware that teenagers are sneaking out to drink and fool around in the woods.
Wham Episode: Hilltop loses its leader when Jesus is killed by the Whisperers, and Negan has escaped his cell with unknown intentions.
Wham Shot: The last walker Jesus is fighting ducks, and then stabs him.
The Worf Effect: Jesus, likely the most physically combat-proficient member of the cast, is killed in one fatal strike by a Whisperer to prove that these new enemies are no easy opponent.
Zerg Rush: After one of their own is killed, a horde of armed Whisperers rushes out to attack the group. When they too fall, a larger group of Whisperers closes in with the herd.
