Devon is staring into a camera and holds a needle containing promicin. She states that she will train her body to produce promicin and develop a 4400-like ability.
Meanwhile, at her apartment Diana, tries to explain to Maia why she can no longer attended school at the 4400 Center. Someone knocks at the door and Diana is surprised to see Ben, since he was supposed to be away. He tells her that he has been offered a job in Spain, and that he would like her and Maia to come with him.
Returning to the house Tess comforts Devon, who is tired from her promicin dose; Devon contemplates what ability she will get. Walking outside onto a balcony Tess and Kevin discuss Devon and the promicin experiment when she begins screaming. Shawn arrives at the house and tries to heal Devon, with no sucess. Tess is on the balcony and spots NTAC agents surrounding the house. Kevin and Tess urge Shawn to come with them but he wants to stay and heal Devon.
At a storage lockup, Richard tells Collier to destroy the promicin in the wake of Devon's death.
Tom and Diana visit Dennis Ryland at HaspelCorp to discuss Dennis' stolen promicin supply. Dennis reveals to them that half of his test subjects who injected promicin, died. Back at NTAC, Tom, Diana, Garrity and Nina discuss the effects of the promicin, and the 50% chance that somebody who injects it will develop a 4400-like ability, or die.
At his home Tom opens his safe, removing the "anti-promicin" injection that he received from the future. He tells Alana that he has to stop Isabelle.
Isabelle and a team of armed men enter a warehouse where they suspect that promicin is stored. Jordan is standing in front of the promicin and Isabelle inflicts pain on him while one of the men test the promicin, but discovers that it is fake. The camera returns to Jordan, who is shown to actually be Boyd Gelder. Boyd states "I have a message from Jordan Collier. It's a new world, and there's no place for you in it." – Boyd presses his finger on a trigger, detonating a bomb, but Isabelle survives the explosion.
Isabelle enters the 4400 Center while Richard receives a phone call from the Center, stating that they believe Isabelle is going to kill people. Isabelle locks herself in a classroom at the Center's school. She approaches Amy Paspalis, and while she talks to her, Maia stands in shock. Isabelle approaches Maia asking if she wishes to take Amy's place, but Maia tells her that what she is attempting to do will not work. Tom and Diana burst into the room, and Diana shoots Isabelle.
Tom approaches Isabelle and attempts to inject her but she wakes up and send Tom and Diana flying in the room.
Richard enters the classroom and tells Isabelle that if she stops what she is doing he will stand by her. She ignores him and continues to inflict pain on Tom. Richard notices the hypodermic needle and uses his ability to levitate the needle and inject Isabelle.
The scene cuts to three days later, where Tom and Alana say goodbye to Diana, Ben and Maia. Maia tells Alana that she will not be there when they return.
"The end of one journey is always the beginning of another. Change is painful, and always comes with a cost. It hurts to bare those costs but we can't allow that to sway us. Tomorrow is a mystery. The only thing we can do is face it with resolve. We move forward, always forward and into what's next. We make a choice, we act on that choice and all it's left is to live and hope."
At a lake, Collier writes into his journal when Kevin approaches and tells him that a woman checked her father, who had Alzheimer's disease, out of a hospital. 4400-like abilities are beginning to propagate.