In Wrigley, Pennsylvania, a group of boy scouts sits around a campfire while being told scary stories by Justin. As he finishes his story, Adam Cross becomes concerned by a humming noise that only he seems to hear and walks off to investigate the nearby area.
The first counselor reassures the kids that Cross is only trying to scare them, until they are alarmed as a mug raises into the air on its own, hanging in the air for a moment with a faint electrical current before dropping back to the ground. This event is soon followed by several screams from Cross and several bright flashes of light from the woods, causing the scouts to take refuge in a nearby truck. Several electrical discharges occur, one of which rips the battery from the truck. The counselor and scouts search the nearby area for Cross only to find his dead body, left ominously floating several feet above the ground.
On the Bus, Phil Coulson is taking several physical tests which Jemma Simmons questions, claiming that he is not due for a physical for another three months. Coulson responds that it was his fault claiming that he got a call from his physical therapist and told her that he had been feeling "rusty".
In the lab, Grant Ward is testing the Night-Night pistol and tells Leo Fitz that it's an ounce too heavy and that it needs to be fixed. After he leaves, Fitz imitates Ward, which amuses Skye. Happy that she is laughing again, Skye claims that after her betrayal she has been doing anything she can to regain the team's trust. Simmons comes in and imitates Ward, as Fitz had done earlier, only for Ward to interrupt, telling the team that they have a new mission.
At the campsite, the team investigates the earlier incident as Fitz and Simmons discover mysterious electrostatic anomalies and examine a hole in Cross' head. As Simmons gets closer to examine Cross' corpse, static discharges from his body before falling to the ground. On the Bus, Skye researches Cross but claims that he is clean of any criminal record, but Ward claims that everyone looks clean on their first "go around". Coulson then tells Ward he's being too hard on Skye but Ward claims that if she wants their trust back she has to earn it, with Coulson claiming that what she had just done is a good start.
In the Interrogation room, Melinda May intimidates the young counselor. Coulson comes down to the lab with Simmons, analyzing the victim's body while Fitz stays out of the lab, expressing a general apprehension and disgust for being around dead things. Simmons shows Coulson the brain of the victim which had been struck by 2,000 megajoules of electricity. May enters and says the Counselor is innocent. Fitz then alerts the team, saying he's detected another electrostatic event.
Coulson, May, and Ward quickly drive to the new location with Skye, pinpointing the event to a farmhouse not far away. Coulson then tells Skye to do a background check on the owner of the farm. The energy signature suddenly disappears with Ward, May, and Coulson arriving too late to save the owner, Frank Whalen. Skye finds out that Cross and Whalen were part of a volunteer fire truck sent to New York City after the Chitauri invasion. The group determines that a killer is targeting them.
Coulson, Ward, and May travel to the local firehouse where Tony Diaz exhibits strange behavior before retreating to the kitchen. Diaz claims to hear a noise similar to the one heard by Cross earlier. Coulson claims that he hears nothing, before noticing a pan lifting in the air. Alarmed, Coulson holds Diaz at gunpoint. May contacts Coulson, reporting her discovery of a Chitauri Helmet.
Coulson asks how they got it, and Diaz claims its a souvenir from their clean up work in New York. He claims that he, Cross, and Whalen were only cleaning it, leading Simmons to realize that Diaz is infected and that the helmet must have had an alien virus on it. Diaz, realizing he is going to end up like his friends, slowly becomes erratic and frightened. Coulson tells Ward and May to evacuate everyone from the building. Coulson stays, and comforts Diaz during his last moments, sharing his experience from his own brief death, before leaving Diaz to his fate.
Later at the fire department, Fitz scans the others to ensure they're not infected while the firefighters are taken into quarantine. Coulson tells Simmons to begin developing a cure. On the Bus, the team is delivering the helmet to the Sandbox, a S.H.I.E.L.D. facility for dealing with biological threats. May assures Coulson he did everything he could for Tony Diaz.
In the lab, Simmons tells Coulson that the infection spreads through electrostatic energy, as a shock. In the middle of her explanation, a lab tool hovers ominously behind Simmons. Coulson apologizes sincerely, and locks her in the lab, as he has realized Simmons is infected.
Coulson reassures his team that Simmons will find a way to cure herself. Coulson contacts Felix Blake to find out more about the virus, but Blake tells them they have no record of it, but in order to save the rest of the team, they must put their infected agent down. Coulson tries to buy time to avoid this protocol by hanging up on Blake.
Quarantined in the lab, Simmons works to test her antiserum on a lab rat, only for it to fail. Fitz and Simmons argue and the two realize that they need the only things to have survived the virus--the Chitauri. They summarize that the only reason the Chituari soldier itself never died from the virus was that it was immune.
Fitz goes to retrieve the helmet and enters the quarantined lab, despite the risk of infection, where the two work to develop the antiserum together. They make a new antiserum from skin cells taken from the Chituari helmet and inject another lab rat with it. It seems to work at first, but it only prolonged the rat's life slightly, as it died moments later. Simmons, having lost all hope and knowing the procedure for these situations, asks Coulson to tell her father first, because her mother will take the news better from him. She then asks for a moment alone with Fitz.
Fitz is not willing to give up and encourages Simmons to keep trying. Despairingly, she knocks him unconscious. Later, Fitz wakes up and finds the rat to be fine, having only been knocked out by the last serum. He sees that Simmons is attempting to save the team by jumping off the plane. Fitz struggles to get through the door as Simmons allows herself to fall from the plane.
Fitz grabs the antiserum and fumbles to put on a parachute to save Simmons. However, Ward grabs both supplies and jumps instead. Ward manages to catch up to Simmons, curing and rescuing her just in time.
In Coulson's office, he reprimands Simmons on the trouble that her stunt caused, and tells her to never do attempt such a feat again, as they would hate to lose her. Later, Coulson reveals to May that he ordered the physical exam for himself, because of his own doubts. She tells him to unbutton his shirt. This reveals the scar left behind by Loki. She reassures him that he feels different because he is different.
In Fitz' room, Fitz is beating himself up over the fact that he did not jump out of the place to save Simmons. She fondly corrects him, telling him that although was Ward did was amazing, it was never Ward who stood by her side in that lab, searching for a cure, and giving her hope when she had none. She assured Fitz that he was the real hero in her eyes.
Later at the Sandbox, Blake tells Coulson that if he keeps pulling stunts like this, the "higher-ups" will take the team away from him. Coulson brushes the comment off, and tells Blake he'd like to see them try. Blake leaves, jovially noting the change in Coulson's disposition.
- Clark Gregg as Phil Coulson
- Ming-Na Wen as Melinda May
- Brett Dalton as Grant Ward
- Chloe Bennet as Skye
- Iain De Caestecker as Leo Fitz
- Elizabeth Henstridge as Jemma Simmons
- Vincent Laresca as Tony Diaz
- Titus Welliver as Agent Felix Blake
- Robert Maffia as Baker
- Rick Gifford as Adam Cross
- David Michael Paul as Justin
- Thomas Robie as Scout #1
- Trevor Larcom as Scout #2
- Caleb Burgess as Scout #3
- Jake Brennan as Scout #4
- Troy Glass as Scout #5
- Tom Crisp as Frank Whalen (uncredited)
- Wrigley, Pennsylvania
- New York City, New York (mentioned)
- Morocco (mentioned)
- S.H.I.E.L.D. Headquarters (mentioned)
- S.H.I.E.L.D. Academy (mentioned)
- Battle of New York (mentioned)
- Chitauri Helmet
- Chitauri Virus
- Tracking Bracelet
- Night-Night Gun
- Anti-Serum Delivery Mechanism
- S.H.I.E.L.D. Satellite
- Dogs (mentioned)
- Captain America
- Miles Lydon
- Iron Man
- Jemma Simmons' Parents
- Typhoid Mary
- The Big Lebowski
- James Bond
- Skye mentioned "The Dude", the main character from the The Big Lebowski who was portrayed by Jeff Bridges.
- The barn used in the scene where the team discovers Frank Whalen's corpse is known as the "Pee-Wee Barn", as it was constructed for the comedy Big Top Pee-wee in 1985 inside Disney's Golden Oak Ranch, in Newhall, California. The barn was later used in episode Repairs.
- When Jemma Simmons shows Phil Coulson the "brain cells", they clearly lack axons/dendrites, which are branchings from the cell walls that make neurons easily identifiable. Brain cells normally use these branches to produce tiny electrical impulses. The cells shown look like red blood cells.