Grant MacLaren begins by inquiring if there are any problems he should know about. Marcy, the previous library employee, vaguely explains that her host's intel was way off the mark but says she is handling it. She does this as she inserts a pretty much invisible communication device into the side of MacLaren's neck so that he can chat with his team. Carly, the tough single mom, confirms that the traveler's neck phones are in working order and all five of them confirm it. MacLaren is impressed that Trevor, the high school football player, was able to build these communication devices. He did it after school, Trevor jokes. Once MacLaren is up to speed, the travelers grab their equipment and promptly head to the exit. But, the beginning of their mission is delayed by the arrival of a squad of gun-wielding police officers who MacLaren apparently called in before his consciousness was swapped out.
In a high tech facility, the sarcastic, intense Dr. Delaney is in possession of powerful antimatter which she created and which is currently contained in a protective facility. However, because the entire power grid is down (due to the blackout) Major Gleason does not think it's safe there. It could result in a deadly explosion and her emergency backups aren't designed to last for more than a few hours. Delaney argues that it's more dangerous to relocate the antimatter especially by untested transport vehicles, but Gleason disagrees. He asserts that any distance they manage to take it is better. When Delaney accuses him of wanting to make a weapon, he politely bids her adieu and walks away.
MacLaren divulges that he was in pursuit of a suspect (Walker, the dead shooter on the ground) who he was forced to take out. Carly also chimes in that there is a cop locked out on the roof, her host's abusive partner Jeff who has followed her there. The female seemingly in charge of the police squad is Officer Boyd. She relieves MacLaren of any further duties by politely "taking it from here" and then hands the FBI agent his containment unit as she introduces herself as traveler 3185. MacLaren is surprised to discover Boyd’s true identity because he thought they were meeting enroute.
MacLaren's team get into a vehicle to go and "prevent an explosion and thus saving the lives of 11,000 people". The explosion will come from the transportation of the anti-matter, that Dr. Delaney was trying to avoid and which Major Gleason caused by irresponsibly transporting the it across town using a giant truck and a small convoy of following vehicles. The containment unit begins to fail and they stop the convoy to try to find a solution.
The travelers are watching Gleason’s every move from their own vehicle. MacLaren and Carly are having a more private rendezvous in their own car. They even turn off their neck phones so the other traveler's can’t listen in. We learn that Carly and MacLaren are a couple.
Back to Gleason. Since an anti-matter detonation now seems inevitable, he orders that everyone to leave the area. Meanwhile, the driver of the truck will haul that ticking time bomb as far away as possible. Gleason ensures that he will be following just behind and that the road ahead will be clear, but doesn't follow and the road isn't clear. Carly stands and blocks the road. The truck driver radios Major Gleason but doesn't get a reply; Marcy takes him by surprise and he's unconscious before he realises there's a problem.
Trevor retrieves the antimatter and the vigilantes leave undetected - just as the driver is waking. When MacLaren reconvenes with his team, Trevor notifies him that they have about 40 hours until they have to host an explosion of their own. In the distance, a much smaller explosion destroys the truck and injures or kills the driver. MacLaren's plan is to hand the antimatter to the arriving leader of a different team and their first mission will be complete. Marcy and Philip volunteer to handle greeting the leader since the rest of the team are busy.
The travelers head to their respective homes. Marcy has a candlelit conversation with her social worker and current roommate David who wants to know why an FBI agent gave him a ring earlier. Marcy avoids the whole truth by telling the part of it, saying that she works with the FBI agent which leads David to making the assumption that she's an agent herself. He also wants to know why she's living with him and she tells him that there will be a time when she will need someone she trusts, and she definitely trusts David.
MacLaren drops Carly off and kisses her before they part. Trevor sneaks up the stairs of his parent's house and bypasses his mom who is running a bath. MacLaren enters his expensive home (for the first time) and, instead of crawling into bed with wife he's never met, he passes out on the couch. Philip drops off the antimatter at the traveler's recently acquired hideout, an abandoned warehouse, and crashes on a floor mattress to sweat out his heroin withdrawal.
In the morning, MacLaren has a confusing kitchen conversation with his wife "Kat", who he mistakenly refers to as Katherine, confusing her. Kat excuses his strange behaviour and says he is not sleeping enough. Trevor is also confused - when he awakes to a teenage erection and his mom strolls into his bedroom unannounced. Carly's morning routine is building muscle and eating baby food. Philip's is vomiting and considering doing a hit of heroin to cure him of his ailments. David wants Marcy to go to the hospital with him due to her having a seizure but Marcy says she doesn’t need a doctor, because she is a doctor. David persists, so Marcy makes a deal. She will go to the hospital if she is wrong about predicting a small commuter plane crash at noon. Obviously, David does not believe her but he does give her a cellphone to contact her later on.
Marcy accepts the gift and heads out to connect with Philip and welcome the team leader they have to give the antimatter to. She does connect with Philip, but unfortunately the team leader's consciousness does not reach his destination; although his host's body wasn't able to commit suicide using a gun he was able to kill himself by swallowing some pills the Director must have been unaware of. When MacLaren finds out that this simple task has become complicated, he panics a little with his team at the hideout. He wonders if the Director has sent them a messenger who would take the form of an adolescent child - but no one has encountered any child messengers. Trevor reminds everyone that the director will assign the team leader to another host. Unless, Maclaren counters, one does not become available in time since they only have 30 hours left. Philip lists off a few soon to be dead candidates but the Director's options do seem to be limited. They brainstorm possible solutions. Philip suggests throwing out an SOS through the FBI so the team can find them while Trevor proposes extending the life of the unit with a supplemental power supply to buy them time.
MacLaren gives the go ahead and leaves to speak with traveler 3185/Officer Boyd. Carly does not think this is a good idea and she is right, Officer Boyd is not happy to see MacLaren. He is breaking protocol 6 and unless he has been authorized by the director to talk to her he needs to step away. She's got nothing more to say other than: In the absence of a clear course of action you await instruction from the director via messenger or traveler. She doesn't know where the team is that's supposed to take the antimatter - and she’s not supposed to know. That is why they are compartmentalized. She ends her advice with "Shit happens" and "Get it right".
Major Gleason and Dr. Delaney are puzzled when he notifies her there was an explosion which put his driver into a coma but that it wasn't nearly as big as it should have been. An antimatter explosion would have been in the megaton range and he speculates that he didn't have the material at all. Either it never existed or Delaney has held onto it. She speculates that he stole it to set off bombs on an island. They agree to disagree and Gleason demands that they speak again later.
David is having lunch at a diner with another client and he sees on the news that Marcy nailed her commuter plane crash prediction. He dials the number of the cell phone he gave her but she's interrupted by an emergency before she can speak. Philip is electrocuted after shorting out a circuit connected to the antimatter because of his hand shaking from withdrawal. David hears Marcy give Philip CPR over the phone before it cuts out on its own. Marcy saves Philip but the short circuit reduced the life of the unit.
The traveler's brainstorm possible fixes from the beginning. Trevor can't make another power supply in the few hours they have. Carly wants to drive it out of town but Philip has a better idea. Bring the antimatter back to where it was created. The whole facility was designed to hold antimatter for an unlimited amount of time. Philip hacks into their main computer system. He can shut down their security and shut down their power but flooding the place will be most beneficial. So, they start prepping to make it rain. As Marcy and Philip suit up, she confides in him that her host was an intellectually disabled woman in the care of the state. Philip thinks this is a huge problem. She replies that she is dealing with it, just as he is dealing with his withdrawal. She encourages him to take some heroin before they leave, to prevent any more problems from shaky hands.
The travelers arrive at the facility with the antimatter, disguised as cleaners there to soak up the flooding in the building. Philip scans the area where they need to be and reports that it is clear. Actually, Delaney is pointing a gun right at Trevor, MacLaren and Carly. Marcy is also pointing a gun, at Delaney from behind. Delaney assumes the traveler's are in cahoots with Major Gleason but MacLaren is honest and explains that they stole it from Gleason to prevent the explosion, and to prevent the military from building the most powerful weapon of mass destruction in history. Delaney is impressed by their portable containment unit and, after MacLaren shows her his FBI credentials, she starts to ease up. Unfortunately, Gleason shows up. In order to get rid of him, Delaney puts on a performance and pretends that he was right. The material never existed. He smugly quips that he enjoyed that confession and wants her to continue her work. As soon as he's gone Trevor stores the antimatter and prevents the explosion.
Delaney now doesn't believe the team are from the FBI and is confident that Trevor's technology does not exist. MacLaren tells Delaney that this won't be the last she'll hear from them and to keep the antimatter out of the hands of the military and off the front page of the newspaper.
Trevor, who missed a science test the day before, returns home to a disappointed mother. Marcy is handed a cup of tea by David who is pleased to hear that she will go to the hospital with him. Carly apologizes to her babysitter for being late and consoles her crying baby. MacLaren's wife Kat is thrilled to hear that her husband is free for the evening. When she goes to pour them a glass of wine, MacLaren answers a knock at the door. His guest is an adolescent child dressed up as a Girl Guide - a messenger from the Director who wants MacLaren to know that the mission outcome was acceptable in light of extenuating factors, but further breach of protocols may result in punitive action. Kat returns with wine and reminds the little girl, who now looks puzzled, that she already bought some cookies from her.