Heads Will Roll

 is the first episode of the second season of Under the Dome.

Synopsis
Barbie's fate is left in the hands of Big Jim and Junior, after being falsely charged with numerous crimes committed by Big Jim. However, the dome releases a mysterious sound, which scares Junior from pulling the lever and causes Linda to halt the execution. The dome has become magnetized, causing execution observers to pass out. Linda, Junior, Barbie and Big Jim visit the dome wall, in which its magnetization pulls all metal objects against it, including Barbie who is still handcuffed. After freeing him, Linda is killed from being crushed against the dome's wall by a large vehicle. Meanwhile, Julia meets Sam Verdreaux (Eddie Cahill), while rescuing a mysterious girl from drowning. Julia leaves Sam and the girl to reunite with Barbie. It is later revealed that Sam is Junior's uncle and Big Jim's brother-in-law. Determined to save the rest of the townspeople, Barbie meets Rebecca Pine (Karla Crome), a high school science teacher who has many theories about the dome. While Barbie and Rebecca attempt to stop the pulses, the others are convinced that the dome is punishing them for not killing Big Jim, when it told them to. The dome's magnetic force locks Big Jim in the fall out shelter, where he seems to be taunted by Dodee's ghost. Eventually he makes it out. Another large pulse has caused everyone inside the dome to pass out, with the exception of Barbie, Julia and Big Jim. Big Jim thinks the dome is telling him to sacrifice himself, but he is unable to reach the lever, so he asks Julia and Barbie for assistance. Julia accepts but then refuses to follow through, sending Big Jim to break it himself. Julia prevents Big Jim's death by cutting the rope, after she becomes convinced that the dome instead wants the townspeople to stop killing each other. Once Julia cuts Big Jim loose, the townspeople begin to wake up and the dome releases all the metal objects. Big Jim tries to gain the townspeople’s trust back by appointing Phil as the new sheriff, and inviting Joe, Angie, Norrie and Carolyn to stay at his house. Later that night, Angie sees the girl who was rescued by Julia and follows her into the school, where she is seen looking into a locker. The girl sees Angie and takes off. Angie looks to see what is inside the locker and is stunned by what she sees. Her shock is short lived however as she is cut down by an unseen assailant, her bloody hand print on the locker the last thing we see. At some point, this mysterious girl is seen near Linda's dead body, saying, "I'm sorry".