Jordan Collier leads Devon Moore, an employee at the 4400 Center, into the basement of one of his safe houses, where Shawn, Richard, Kevin, and Tess stand waiting. Devon has volunteered to inject herself with promicin and allow them to film it. A few hours later, at NTAC, Tom and Diana watch Devon's video, which is being downloaded off the internet in record numbers. Before injecting herself, Devon explains that shots of promicin will soon be available to everyone, and that ordinary people developing abilities is the key to a better world. Tom comments on the coincidence that one of Collier's employees is injecting herself with promicin just a day after Haspelcorp's stockpile of the substance was stolen.
Tom and Diana, with a team of NTAC agents, search the 4400 Center but find no sign of Devon or the stolen promicin. Tom and Diana question Jordan Collier, but he claims that he had nothing to do with the video and doesn't know where Devon is. As for the stolen promicin ... NTAC doesn't have any proof that Jordan was involved. Before leaving the Center, Diana goes to Maia's classroom and pulls her out of school.
Back at Diana's apartment, Maia argues with her mother about being taken out of school. But Diana explains that the 4400 Center isn't safe. Just then, there is a knock at the door. It's Ben Saunders. He tells Diana that he is leaving for Spain for six months and wants her and Maia to come with him. Diana says she'll have to think about it.
Meanwhile, at the safe house, Devon starts to go into convulsions. Kevin and Tess send for Shawn, who rushes to the scene. Shawn tries to heal Devon, but she dies. Just then, NTAC bursts through the door. They were able to use clues from Devon's video to determine her location. Kevin and Tess get away, but Shawn is too overwhelmed by Devon's death to attempt escape. NTAC takes him into custody.
Jordan, Richard, Kevin, Tess, and Boyd Gelder meet at the abandoned airplane hanger where the stolen promicin is being stored. Richard argues that they can't distribute the promicin if it's possible people could die. Jordan argues that Devon's death is one of many sacrifices that will be necessary to build a better future -- They can't stop now. Richard uses his telekinesis to try and destroy the vials of promicin, but Tess uses her ability to compel him to stop.
Tom and Diana go to Haspelcorp and ask Dennis Ryland why someone would die from taking promcin. Ryland reveals that half of the volunteers who took promicin in the super soldier program died within the 48 hours. Anyone who takes promicin has a fifty-fifty chance. Tom asks Ryland why he withheld this information after Haspelcorp's supply of promicin was stolen. Ryland explains that he wanted to discredit Collier. If people start dying, the general public will no longer see Jordan as a savior.
Tom and Diana head back to NTAC and explain to Shawn that people could die if promicin hits the streets, but Shawn refuses to betray Jordan. Suddenly, Ryland shows up with Isabelle and a military escort. The government has given Ryland permission to take over Shawn's interrogation. Ryland sends in Isabelle to interrogate Shawn. Shawn asks why Isabelle is working with Ryland. Isabelle explains that her mission was to destroy the 4400, and she didn't want to do that. Despite what Shawn thinks, she does care about him. Isabelle thought if she gave Ryland promicin, there would be a standoff -- a cold war. If everyone has the technology no one will use it. Shawn refuses to give up any information so Isabelle is forced to torture him. Isabelle gets the information she needs but puts Shawn in a coma in the process.
Ryland, Isabelle, and a group of soldiers reach the airplane hanger where the promicin is being stored. Isabelle enters with the soldiers and finds Jordan Collier by himself, standing in front of the stacks of stolen promicin. One of the soldiers tests the promicin and tells Isabelle the entire stockpile is fake. Isabelle looks back at Collier to find that he is in fact Boyd Gelder. Boyd used his 4400 ability to impersonate Collier to draw Isabelle in. Boyd then holds up a detonator and presses the button. Suddenly the entire hanger is engulfed in flames. Outside, Ryland is thrown back by the explosion. Isabelle soon emerges unscathed and tells Ryland that she is going to go to the 4400 Center and start killing people to draw Collier out. Ryland tells her that she can't just go killing people at random in broad daylight. But Isabelle ignores him and walks away.
Meanwhile, at an underpass, Jordan hands out backpacks full of vials of promicin to a group of homeless people who have committed themselves to his cause. Jordan instructs them to let people know the risks of injecting promicin before handing it out. People must be allowed to make a conscious choice.
At the 4400 Center, Isabelle enters a classroom full of children, including Maia. Maia snuck back to school without Diana knowing. Isabelle is about to attack, when Diana busts through the door and shoots Isabelle several times. Tom runs over to Isabelle and attempts to inject her with the syringe the future gave him. But Isabelle quickly comes to and tosses Tom to the other side of the room. Isabelle then incapacitates Diana and attacks Tom. As Isabelle strangles Tom, Richard enters and uses his telekinesis to pick up the syringe and inject Isabelle. Although it does not kill her, she no longer has any abilities. Unsure if it is just temporary, Tom shoots Isabelle in the shoulder to make sure she can't heal herself and that her powers are really gone. A few hours later, Tom learns that Isabelle made it out of surgery okay, but no longer has any promicin in her system.
Three days later, Diana comes by Tom's house with Ben and Maia to say goodbye. Diana has decided to go to Spain with Ben. Although Tom will miss his partner, he understands Diana's need to raise her daughter in peace.
Elsewhere: Kyle sits in a motel room getting ready to inject himself with promicin, NTAC closes the 4400 Center, Alana is abducted in a ball of light, and April Skouris stands in line to get a shot of promicin.