Imminent threats prompt reflection. We're forced to take stock of our lives: the things not done, the words not said, the actions not taken. That's where "Morning Star" leaves those at Hilltop. Alpha and her horde are on their way. With no means of escape and few defenses compared to the heat she now brings to their doorstep, Daryl, Carol, Ezekiel, Rosita, Eugene, Lydia, even Alden have moments of intense, emotional thought. They might not survive the night, and that lends more weight to when they do finally decide to connect to each other. Coincidentally, this episode arrives at a time when the real world is preparing for the impending spread of coronavirus and an asteroid that we thought at first might hit earth (but it won't). All around, it feels like a time to do the things you want to do while you have the time to do them.
The Whisperers, which now include a masked Negan, fill bags with flammable tree resin and begin marching the horde to Hillside, just as Aaron, Judith, RJ, Rosita, and Mary arrive. Daryl and Lydia, who were out scouting for an entrance to the cave, ride up soon after to warn everyone. Those at Hilltop can't stay. They don't have enough fighters to face those kind of numbers. Neither Alexandria nor Oceanside would be able to make it to them in time to help. But they also can't leave. The Whisperers cut down trees over all the roads leading in and out of Hilltop. They are trapped and alone. They have no choice but to fight.
The story weaves through various viewpoints as these characters come to terms with what is about to happen.
Eugene is developing feelings for Stephanie, the woman he met over the radio (who's from the Commonwealth but we're not supposed to know that yet). They continued to talk in secret without alerting their respective communities, and while talking about observing satellites falling to earth, they realize they are closer than they think: they both saw the same satellite fall, which means there's at most a few hundred miles between them. Rosita, however, walks up to the attic and hears Stephanie's voice over the radio when Eugene isn't there. Rosita tries speaking with Stephanie and ends up spooking her off. Eugene lets Rosita think it's some woman from Oceanside that he's falling for, and she helps him work out his feelings. Later on, while Eugene is singing to Stephanie, she asks him to meet her in Charleston, Va. in a week's time. He promises he'll be there, but first, he has to deal with the approaching horde.
Mary wants to see Adam, her nephew, but Earl isn't about to let a Whisperer, a reformed one or otherwise, see his son. Alden takes a surprisingly staunch stance against Mary, but it's understandable when you remember his still present grief over losing Enid. They're fighting to preserve the future they built for kids like Adam, and he feels it to be a disgrace to Tammy's memory to hand over Adam to Mary. But Mary, too, doesn't know how long she has left to live, which is something "Morning Star" doesn't really get into. She's just forced to pick up arms herself and fight.
Carol also begins her apology tour, or as close to one as we're going to get from Carol. She mends her relationship with Ezekiel and learns about his cancer. She also makes nice with Lydia. Carol promises to kill Alpha, and though Lydia mentions this won't save them, she says it will feel good. Off in the woods, Negan uses similar verbiage with Alpha. He says killing Hilltop, Alexandria, and Oceanside will feel good, but will feel even better is forcing them to surrender and growing her numbers. Neither Alpha nor Carol want to the latter option. They want the instant satisfaction of slaying their enemies. Carol and Daryl finally buries the ax with help from their loved ones. Carol spies a painting of what appears to be Glenn hanging on the wall before going to meet Daryl, who's staring at the graves of their fallen friends. She asks him to not hate her, to which he replies, "I'm never gonna hate you."
As Hilltop prepares what defenses they have, a swarm of rats rush forth from the tree line, signaling the arrival of the horde. Daryl and Ezekiel make a pact: if one of them falls, the other will get the children to safety. Judith wants to fight, but Daryl fears for her. So, instead, she stays back and calls out to Michonne over the radio. (Might this signal the character's return with whatever she finds on that island in the next episode?) Wearing a new vest, featuring a blue angel wing that Judith patched on, Daryl walks out to the front lines. The battle begins when the horde arrives at dark. The first line of defense is an electrical wire strung up around the field that leads to a truck battery. Its heat cuts through some of the dead, but the horde is too immense and quickly crumbles the contraption. They then hit the next barrier and everyone rushes to kill as many of the dead as possible. Then, the Whisperers themselves strike. They launch those poaches like cannonballs, coating the Hilltop army in resin. Flaming arrows follow to ignite the battlefield and some of the soldiers themselves. They are forced to retreat but more arrows ignite the very walls of Hilltop. Like the community itself, Daryl and his forces are trapped, unable to flee and unable to fight. They are alone.