Warning: this story contains spoilers for Sunday's "Mourning Cloak" episode of Fear the Walking Dead. The lifespan of the average butterfly is tragically short. "They only live for a year, tops," says Ali (Ashton Arbab), a Ranger in training sent by Howard (Omid Abtahi) to collect the rare Mourning Cloak butterfly for Victor Strand (Colman Domingo). Unlike most butterflies, the Mourning Cloak has a lifespan of about a year. Asks Charlie (Alexa Nisenson), "Don't you think that something like that should get the chance to live, even if it's just for a little while?"
On the eve of her 13th birthday, Charlie gets caught trying to sneak into Strand's Tower for "a chance at a normal life." Suspecting Morgan (Lennie James) sent Charlie as a saboteur, Howard orders 15-year-old Ranger cadet Ali to learn the real reason Charlie arrives at the Tower weeks after Alicia Clark (Alycia Debnam-Carey) declared war.
Wanting a place in the Tower, Charlie volunteers for a risky mission to find the parts needed to repair the elevators damaged by Arno (Spenser Granese) and the Stalkers. Escorted by Ali, Charlie goes alone inside the walker-filled building where Ranger Garcia (Matthew Ramirez) suffered radiation burns.
After some bowling bonding, Charlie retrieves the replacement elevator circuit board and tells Ali the truth: Morgan sent her to disable the beacon on the Tower roof so they can clear out the walkers below and free Grace (Karen David) and Baby Mo. Because of her developing feelings for Ali, Charlie says she's not going through with Morgan's plan.
Ali locks Charlie inside the elevator shaft and leaves her alone to escape a pack of walkers. But Ali relents and returns for Charlie, telling her they can run away together and not get caught in the middle of Strand's war with Morgan. They kiss, and Charlie suddenly passes out.
At the Tower, nurse June Dorie (Jenna Elfman) reveals Charlie was exposed to radiation inside the building. "Given the amount of exposure she's had," a tearful June reports, "she should make the most of every day."
After midnight, Ali sneaks Charlie into Strand's conservatory, where he's freed the captive butterflies as a birthday gift. "You were right," Ali tells Charlie. "Something this beautiful deserves to live, no matter how long that is."
After promising to take care of the light, Ali sneaks to the roof to shut off the beacon. Howard catches Ali and throws him from the roof because "it's what Victor would do." Charlie cries as she watches her boyfriend fall from the Tower roof to the walker horde below.
Howard threatens to do the same to Charlie but backs down when June reminds him Strand's Tower needs someone with medical training. Accepting blame for failing to stop Charlie from going inside the building, June makes her a promise: "No matter how much time you have left, you will live to see Strand go down. I will do everything I can to make sure that happens."
On AMC+'s Fear the Walking Dead: Episode Insider, showrunner Ian Goldberg confirmed Charlie will soon succumb to radiation poisoning.
"Charlie and Ali connect right away for one simple reason: they're both young people in the apocalypse. They had to grow up way too fast," Goldberg said. "Neither of them have been able to have this kind of connection, you know, that sort of first love, butterflies in the stomach kind of feeling. And Ali helping her learn how to bowl is huge for her because it makes her feel like a kid, it makes her feel alive. It's not just surviving. She's actually living."
Goldberg added, "I think Ali recognizes as well that even though Charlie came to the tower with some negative intentions from his perspective, ultimately, it was all because she wants to have this normal life. And that's why Ali turns around, because he understands Charlie in a new way."
After Charlie's diagnosis, their talk about the butterflies is "front and center at Ali's mind, because he's realized Charlie's a bit like that butterfly now," Goldberg explained. "She is someone to him that is beautiful and is going to have a very short life because of her radiation exposure. So I think him freeing the butterflies is an act of wanting to show her how much he cares about her, but also because it really is a metaphor for Charlie."