Fog of War is the sixth episode of the second season of The 100. It is the nineteenth episode of the series overall.
Tensions run high between Clarke and Finn while Raven discovers that Mount Weather is interfering with their communication systems. Meanwhile, Jasper and Monty discover the truth about what is going on at Mount Weather and Octavia comes face-to-face with her worst nightmare. Finally, President Dante Wallace is about to be betrayed by those closest to him.
Two days after the massacre at Lincoln'svillage, Clarke and Bellamy are sitting outside in the bar area of Camp Jaha. They are reviewing Clarke's map of the tunnels through Mount Weather and are discussing an action plan to get the Delinquents out. Finn and Murphy approach and Clarke admits she has not talked to Finn since they got back. Bellamy leaves to get drinks and Finn asks about the Mount Weather plan. Murphy tells Clarke they were cleared because the pardon the Delinquents received for being sent to Earth includes their time on the ground. Clarke still will not really talk to Finn so Finn leaves. Raven arrives and tells Murphy to leave before she reveals to Clarke that she figured out why they had not heard from any of the other stations: Mount Weather has been jamming their signals. Major Byrne witnesses the conversation and tells Abby about the new development. Later, while Raven is explaining to Clarke how Mount Weather has been jamming their signals and even crashed the Exodus dropship that came down on Unity Day, Abby interrupts them and tries to stop them. Clarke and Raven convince Abby that they need to take down the radio tower on Mount Weather so they can find any other Ark survivors to help build their army. Abby tells Byrne to stay behind and guard the camp because Abby will be going with them to Mount Weather.
Meanwhile, at Mount Weather, Dr. Lorelei Tsing is trying to convince Dante Wallace to allow her to continue experimenting on the 47 Delinquents. Dante refuses and tells Cage Wallace that if he gives the order to Harvest the kids, then he will not deserve to see the Earth again. He leaves, saying he is going to find volunteers instead. Cage and Dr. Tsing plan that if there are no volunteers, then they will proceed anyway.
Clarke, Abby, Raven, and several other Sky People are hiking to Mount Weather to take out the radio tower. Clarke and Abby discuss Finn's situation and how the Council cleared him.
Kane and Jaha are both trapped in a Grounder prison. Jaha tells Kane that their time is not up yet because they still have work to do. Gustus enters with some warriors and they start to beat up Jaha. Kane tells them they came in peace. Gustus tells them about the massacre in Tondc and says that "blood must have blood". He leaves behind a dagger and tells them that one of them will die by the other's hand and only then will he hear the terms of their surrender. He leaves behind a girl, Lexa, to make sure the deed is done. Lexa tells them that if they refuse to do it, the Commander will use the knife to slit both of their throats.
As Jasper is released from Medical, Dante approaches him and explains to him about the radiation problems the Mountain Men deal with and how their current methods pale in comparison to the Delinquents' blood. He asks Jasper to try to get his fellow Delinquents to volunteer to help out the Mount Weather residents.
Clarke, Abby, and Raven have stopped to survey Mount Weather and look for the radio tower. Abby realizes that Bellamy and Octavia have taken off on their own to find another way into Mount Weather. She sends Sgt. Scott and two other Ark Guards off to go find them. Finn volunteers to go after them, too, but Clarke stops him. Finn gets upset because of the way everyone is acting toward him since the massacre and storms off with Clarke following after. Acid Fog suddenly starts rolling toward them and Clarke and Finn take off for the bunker.
Bellamy and Octavia are looking for another way into the mountain when Sgt. Scott stops them and tells them to come back. Critters start scurrying across their feet and Bellamy realizes that the Acid Fog is coming. Octavia follows the bugs and discovers a hidden door leading to an underground parking garage. Bellamy and Octavia rescue Sgt. Scott and one of the Ark Guards but the other guard is swallowed up by the fog.
When Clarke and Finn get to the bunker, Clarke sees Delano's corpse still sitting there. Finn covers it up.
Abby and Raven have taken cover in a tent from the Acid Fog as Raven attempts to get a signal. She picks up an encrypted channel and realizes they will be able to listen in on Mount Weather.
In the parking garage, Sgt. Scott gives Bellamy a gun and he and the other guard split up from Bellamy and Octavia.
Clarke and Finn discuss the awkwardness between them and Finn gives Clarke back her father's watch that had been around the dead Delano's neck.
Jasper is trying to convince the other Delinquents to volunteer to give blood but no one wants to. Monty tells Jasper that he is going after Clarke just as Maya enters. She starts talking to them about "pizza day" while holding up a pad of paper saying that "they're listening" and to follow her. She takes Monty and Jasper to a storage room where it is private and explains to them that she found out the breach was not an accident. She then reveals to them the Harvest Chamber and that she is scared they are going to be next. She explains to them that without the treatments, everyone would die. Monty wants to try getting out like Clarke did, but Maya says it will not be possible now since security has been increased. Jasper says that for now, they need to buy some time by volunteering.
While they are still trapped by the Acid Fog, Raven breaks the encryption on the radio channel and they overhear the Mountain Men discussing "the veil". Abby tells Sgt. Porter to get ready to blow the radio tower to find out if there are any other Ark survivors, but Raven tells her if she does blow the tower, then they will not be able to listen to the enemy anymore and that she knows what Clarke would do.
Sgt. Scott and the other guard are looking around the parking garage and into cars. Sgt. Scott finds a wind-up toy that plays Christmas music. They are suddenly attacked by Reapers. Bellamy and Octavia hear the screams and go to investigate where they find two Reapers eating the Ark Guard. Bellamy shoots them both before they find a third Reaper hovering over Sgt. Scott's body. Octavia recognizes it as Lincoln and calls out to him but Lincoln attacks her. She shoots him in the leg and Bellamy knocks him out and they flee.
Kane and Jaha discuss the difference between murder and sacrifice as they decide whether to follow Gustus' orders or not. Kane picks up the dagger and offers it to Jaha, telling Jaha to kill him; however, Jaha refuses. Kane then cuts his own wrist and Jaha begs Lexa to help him. Lexa tosses him a bandage before Jaha takes her as a hostage.
Bellamy and Octavia are hiding in the back of an abandoned car, discussing what they're going to do with Lincoln. Bellamy promises Octavia that they will get Lincoln back.
Gustus and the guards enter where Jaha is holding Lexa hostage. Lexa then takes out Jaha and holds the knife against his throat before revealing that she is, in fact, the Commander. She says that Jaha will be used to send a message and they drag Jaha away because "the massacre must be answered".
Octavia lures Lincoln to her and Bellamy uses the Ark Guard's shock baton to knock Lincoln out. He then tells Octavia that they're taking him home.
As the Acid Fog lifts, Clarke tells Finn that she doesn't know who he is anymore and he says that he does not either.
Back at Mount Weather, several of the Delinquents are "volunteering" for harvesting. Dante tells Dr. Tsing and Cage that all they had to do was ask. Dr. Tsing leaves and Dante grabs hold of Cage, telling him that he knows about the breach and if he finds out Cage had anything to do with it, then Cage would never assume the presidency after Dante.
The Delinquents are recovering in their dorm as they discuss waiting on Clarke to break them out of Mount Weather.
Once Clarke and Abby meet back up at Camp Jaha, Abby tells Clarke that they decided against blowing the radio tower because they're not sure if there are any Ark survivors but they are sure that there are 47 Sky People trapped in Mount Weather. Just then, Jaha approaches and tells them he has a message from the Commander: "leave or die. We have two days".
This episode reveals that Finn killed 18 Grounders in the massacre he committed in Human Trials.
This, plus the Grounder he shot and the Reaper he killed in season one, places Finn's death count at roughly 20 people killed by his own hand. This makes him the Delinquent with the highest death count.
The scene where Finn says "It was an accident" wasn't a reference to the massacre. It was actually a reference to Raven.
In a deleted scene, Finn pulled away from Raven and she fell down because she only has one good leg. Jason and the editors removed the scene for various reasons, however, they forgot to edit out Finn's line.
There was a scene written where Clarke and Finn bury Delano's body, but it was cut.