The most essential component of The 100‘s Bellamy Blake is that he is a big brother. Octavia’s birth defines him from the moment that it happens; everything he does from that point forward is for his little sister. Since the Blake siblings are the only siblings on the Ark (that the audience knows of), their relationship is incredibly unique.
We see other familial relationships on The 100, of course. Clarke and her mother Abby have a complex relationship, largely because of Abby’s role in her husband’s death; Monty is reunited with his mother after thinking her dead for months, only to have to kill her when she enters the City of Light. But there are no other siblings, not even amongst the Grounders. The Blake siblings rely on each other in a way that is exclusive to them, even when they are totally at odds.
Octavia, forced to live under the floorboards on the Ark for most of her life, chafes against Bellamy’s protective nature from the moment the delinquents set foot on Earth. She wants to kiss boys, explore the planet, and do her own thing. Bellamy wants her to stay at camp and stay safe. It’s a messy, intricate relationship, and as it unfolds, one thing becomes apparent: Bellamy will do anything to keep his sister safe.
It doesn’t matter who he has to kill or what atrocities he has to commit. If Octavia is in danger, Bellamy will do what’s necessary to get her out.
Season four has complicated that. Octavia blaming Bellamy for Lincoln’s death and consequently taking her anger out on him with physical blows forced a massive rift between the Blake siblings. His repeated attempts to earn her forgiveness are shot down and she never apologizes for beating him to a pulp, nor does she ever outwardly acknowledge that he didn’t kill Lincoln.
That’s honestly really gross, but it also follows an established pattern: Bellamy will do anything for Octavia. Octavia will do anything for Lincoln. That includes trying to disown her brother.
Until Octavia left Skaicru’s camp and Bellamy realized he would never be able to find her (or survive the attempt, with black rain falling nearly all the time now), he tried, and tried, and tried to make her see reason and forgive him for the part he played in Pike’s reign. Then he accepted that “you can’t save someone who doesn’t want to be saved” and turned his attention toward surviving himself.
Then Octavia came back, without Bellamy having to find her at all.
Supportive Big Brother Mode was once again enabled when she prepared to fight in the conclave, and he reminded Octavia that in order to win, she didn’t have to kill everyone. She just had to be the last person standing. Surprisingly, it was advice she took. And it worked.
Recalling her hiding skills from when she lived under the floorboards on the Ark allowed Octavia to keep mostly out of sight of the other warriors until the end of the battle. Hiding even enabled her to kill Luna, whom everyone was afraid would win the conclave. If she had, the human race would have been kept out of the last remaining bunker forever.
Instead, Octavia won, only to discover that Skaicru had secretly stolen the bunker — leaving her, Kane, and all the clans Octavia had promised spots to — locked out.
Bellamy, because Clarke had him knocked out and taken to the bunker while he was unconscious, is inside. Octavia and Kane were supposed to be inside as well; Clarke dispatched people to capture all of them. However, the plan failed; only Bellamy made it into the bunker before Skaicru closed the door.
Although separating the Blake siblings was unintentional, it was the worst move Clarke, Jaha and the rest of Skaicru could have made. Bellamy has always done whatever he had to do in order to save his sister. Letting her go earlier in the season was a decision that seemed to take everything out of him, and his relief at seeing her again in Polis — even though she meant to fight in the conclave — was palpable.
Opening the bunker door to get to Octavia, of course, endangers Skaicru. For once, rather than killing hundreds of grounders or mountain men to save his sister, Bellamy has to save those people. Opening the door to the bunker means admitting not only his sister (and Kane), but admitting 100 people from each clan so that the human race can all survive; not just Skaicru.
Jaha and Clarke both try to prevent Bellamy from opening the door by literally chaining him in a locked room. Everyone knows that when it comes to Octavia, Bellamy can’t be stopped. He’ll do whatever he has to do to save her, so long as she wants saving.
In this case, even being chained up won’t stop him. He rips apart his wrists and hands trying to get out of his restraints. He screams and pulls and begs Murphy to let him go, seemingly so he can open the door to the bunker himself. But Bellamy is smart. He enlists Abby’s help, knowing that she’ll be sent down to treat his wounds and also knowing that she doesn’t want Kane to die on the surface while she’s safe inside the bunker.
Meanwhile, Octavia waits on the surface, knowing that Bellamy will come through. He always has.
It’s a sequence reminiscent to season two, when Bellamy went inside Mt. Weather to find the delinquents that were being drilled for their marrow. Except this time, instead of Clarke waiting for updates, it’s Octavia. This time, Bellamy has to act against Clarke in order to save his sister. The Blake siblings are messy, but Octavia is Bellamy’s whole world.
His sister, his responsibility. Nothing else matters but that.
Given how ruthlessly Bellamy has tried to help Skaicru survive in seasons past, this episode reads like a reversal. The main behavior is the same: protecting Octavia no matter the cost. But by opening the door, Bellamy accepts that Skaicru will have to send many of its own people to the surface in order to make room for the other clans.
The human race will survive as a whole because the Blake siblings ended up on opposite sides of the bunker door. Their relationship, because it is so unique, has always had a unique impact on greater events within the plot of The 100. The bunker is no exception.
Bellamy’s redemption arc has been long and unnecessarily drawn out. Opening the bunker door felt like a reversal of all the decisions he made in seasons prior, especially season three. Although his main goal was the same as always — saving Octavia — he also literally opened the door to survival for the rest of the clans. It felt like an important reversal of his past choices, and a really important moment of growth for him as a character, especially because it required him to stand against Clarke.
Seeing how the Blake siblings heal their relationship moving forward will be huge and, hopefully, a focus of series five. They have a lot of work to do; I hope the writers give them the space and time to do it.