Warning: SPOILERS ahead for The Handmaid's Tale season 4, episode 3, "The Crossing."
The Handmaid's Tale season 4 doesn't pull punches with its opening salvo of episodes, killing off characters who've been in the show from the start. In episode 3, "The Crossing," June and five other captured handmaids make an escape attempt that leaves only June and Janine alive. Alma and Brianna, two characters who made their debut in The Handmaid's Tale season 1, are killed suddenly and shockingly when they're hit by a train - adding more names to the growing list of deaths that June blames herself for.
Although June is perceived as a symbol of hope and resistance among many of the people in Gilead, there's also another side to her rebellious behavior. As Moira points out while trying to place the children from Angel's Flight with families in Canada, June's bold actions often leave other people struggling to deal with the messy aftermath. In The Handmaid's Tale season 2, June was left traumatized after a family who tried to help her escape Gilead were brutally punished: the father executed, the mother forced to become a handmaid, and their child sent away to live with another family. To bring June back in line, Aunt Lydia drummed into her that everything bad that had happened was "your fault."
The deaths of Alma, Brianna and the other handmaids - as well as the Marthas Beth and Sienna, who were pushed off the top of the prison when June refused to speak - add weight to the already enormous amount of guilt on June's conscience. This is pressed home by Aunt Lydia, who is present during June's interrogation process to reiterate the "your fault" mantra. The Handmaid's Tale season 3 ended on a moment of triumph for June as she successfully smuggled 86 children out of Gilead, and the first two episodes of season 4 continued to build up feelings of hope. "The Crossing" is a sobering reminder of just how powerful a force Gilead is, how brutal and sadistic its leaders are, and how terrible the consequences of rebellion can be.
As sad as it is to see Alma and Brianna die instead of escaping Gilead or continuing to fight for Mayday, there are reasons why their deaths were necessary for the show from a storytelling standpoint. June has escaped several times already and this latest escape attempt already stretched suspension of disbelief with how easy it was (only one Guardian and one Aunt watching over six of the most notorious rebels in Gilead, and the van door not even being locked). Not only would it have been incredibly convenient for the train to pass just in time for everyone to get over the tracks without being followed, there also needed to be a heavy cost not only to the act of escape, but to June's decision to sell out the other handmaids. Showrunner Bruce Miller explained in an interview with Variety:
"I wanted it to have a cost for June right in front of her because honestly when people say something’s going to be hard and then it turns out to be hard, everybody’s shocked [by] what hard feels like. But this is what hard feels like: you make decisions and people can die in front of you and you are nothing but full of regret and mistakes and that doesn’t go away. Her journey out of Gilead is very hard, and although we show a lot of those trials and tribulations, we are very nice, compared to what those situations are in actual life."
Before the handmaids made the collective decision to attack Aunt Lydia and make a break for it, there was an intense but silent exchange between them in which they all seemed to come to the same conclusion. Rather than being executed for their crimes against Gilead, the handmaids were being taken to a Magdalene colony - presumably inspired by the Magdalene Laundries in Ireland, which were rife with abuse of the "fallen women" who were sent to them. Gilead's Magdalene colonies are effectively breeding colonies, with commanders and their wives brought in to perform "the ceremony" with the handmaids on their fertile days, and the rest of the time spent in hard labor in the fields.
June herself told Aunt Lydia that she was ready to die while in prison, and the rest of the handmaids seem to have reached the same conclusion: that they'd rather die free than live in service of Gilead. Though Alma and Brianna may not have made it to freedom, they still escaped their sentencing to the Magdalene colonies - and got to strike one final blow against Aunt Lydia.