The 100 Season 2 Episode 10 is titled "Survival of the Fittest" and it aptly opens with Lincoln and Bellamy, definitely two of the most fit for survival. They are on the road to Mount Weather and are entering full battle mode as Lincoln rubs animal blood on his face as his reaper disguise.

Bellamy obviously ships Linctavia, telling Lincoln that he is good for his sister. In the process of this bonding, we get a bit of Lincoln back story, learning that as a child he saw a ship fall from the sky and was forced by his dad to kill the occupant. This led him to save Octavia before he really knew who she was.

Back at Camp Jaha, Kane welcomes Indra and the Grounder warriors for joint training. Jaha has been pardoned, but he is not on board with this new development. Meanwhile Clarke and Lexa are brainstorming a plan of attack for Mount Weather, but there is dissent among the new allies.

Murphy gets into it with a Grounder, punching him after he references Finn. Similarly, grounder warrior Quint refused to align with Clarke because she was responsible for the death of his brother.

As Lincoln prepares Bellamy for his entry into Mount Weather, he reveals that he remembers everything about being a reaper, a disturbing revelation given his reaper actions. 

Meanwhile, Jaha enlists Murphy to take him to his son's unmarked grave. 

During target practice, it comes to light via Octavia that Grounders can't use guns because of threats from the Mountain Men. Octavia is unhappy that she is not allowed to participate in training, and it becomes clear that she is extremely knowledgeable about the Grounder way of life.

After she is attacked by the vengeful Quint, Lexa saves Clarke's life. But something else is out there killing. When it comes for them, Lexa disables Quint, leaving him as a decoy to buy time for the others to escape. They find themselves in a feeding ground for an unseen beast. Turns out it is a hard-to-kill Gorilla with super strength. Lexa hurts herself during their escape and Clarke helps her to safety.

Murphy is leading Jaha to the drop ship, becoming agitated when Jaha calls him "son." It turns out Jaha was responsible for sentencing Murphy's father to death for stealing medicine, which he only did to save Murphy.

Back at Camp Jaha, Octavia is ready for a fight and she is not taking no for an answer. She challenges Indra and is ultimately given her fight with a Grounder warrior. She is outmatched but fights hard and does not stay down. It is clear she has the heart and mind to become a fierce warrior, should she be allowed to train. Indra respects Octavia's strength of spirit and takes her under her wing, offering her the position of her second. 

Lexa thinks Clarke is weak for not leaving her to die. Clarke tells her that it is not weakness, but only necessity, because she fears what will happen if one of her guards becomes Commander next. Lexa says that their spirits choose the next Commander, prompting her to wonder how the Ark chooses their leaders. Is it any less random? The two manage to lock the gorilla in the room and escape.

Jaha is trying to relate to Murphy and shares with him the story of the City of Light. Murphy is skeptical, but Jaha says he plans on finding it and leading the Ark survivors there. He has assembled a group to accompany him on his quest to find the City of Light. He wants Murphy to join them, although he doesn't know where he is going, has no map to get there and is venturing out on faith alone. 

Lexa and Clarke discuss Mount Weather, and Clarke is confident that Bellamy is their best chance once he is inside.

Unfortunately, Bellamy and Lincoln's plan hits an unprecedented detour when the pull of the reaper drug proves to strong for Lincoln. He submits to the injection, killing their plan and leaving Bellamy at risk. Bellamy is marked for harvesting and if the preview for next week's episode is any indication, things do not look good for Mr. Blake.