|"I Believe the Children Are Our Future" begins with a string of deaths in Alliance, Nebraska that result from childish pranks gone wrong. Itching powder takes the life of a babysitter, who literally scratches herself to death (yuck!) Sam and Dean come in to investigate, only to have the little boy in the house confess to using the itching powder. The boy feels very guilty.
Next, a death in a nursing home results from a joy buzzer. Sam and Dean take a look at this death, too, and Dean tests out the killer joy buzzer on a ham. The ham is actually cooked by the joy buzzer, so they decide to go to the deadly toy's source -- the joke store. The owner is suspicious, in that he seems to dislike his younger customers, but the deadly joy buzzer freaks him out, so it seems obvious he didn't make it.
Next, the deaths seem to change their pattern from pranks, but are still related to childhood. A little girl, scared to go to sleep because the idea of the Tooth Fairy bothers her, puts her tooth under her father's pillow. This results in a giant man (in a tutu and wings) waking the father in the middle of the night. He goes after the dad with a pair of forceps. Next thing we know, dad is in the hospital and has earned himself 32 coins -- one for each forcibly removed tooth!
At first Sam and Dean think this is the work of Trickster. However, they look at a local map and realize that the center of all these deaths is a farmhouse. The plan to head out there, but not before Dean reveals that he now has hairy palms. D'oh! We all know what causes that...
At the farmhouse, Sam and Dean find little Jesse, an 11-year-old boy. Jesse is the cause of all these deaths, which are resulting from Jesse's imagination. When the boys convince Jesse that joy buzzers are harmless, they test the killer toy again and nothing bad happens. With a bit of research, it turns out that Jesse was actually adopted. So, who is the mother? A woman named Julia, who was possessed by a demon throughout her pregnancy. Little Jesse is a hellspawn.
Castiel then shows up to break some bad news to the Winchester boys -- Jesse isn't just a product of evil, he's the Antichrist himself. Apparently, the Antichrist doesn't have to be the direct son of Satan, but just an offspring of any demon. Cas wants them to kill Jesse, as he could be used as a weapon for Lucifer. The boys are obviously reluctant, so Cas goes in to do the job himself. Sam and Dean show up at Jesse's house just in time to find him turning Cas into an action figure!
The boys try to stop Jesse's path of destruction by convincing him he's a superhero and that he needs to come with the boys. Then, Jesse's real mother Julia shows up. She's possessed by the demon that was in her while she was pregnant. She tells Jesse that the boys are lying, so the boys 'fess up to what's really gone. They want him to come with them and to make the right choice not to be evil. Jesse takes the demon out of Julia with just a wave of his hand, then tells the boy he wants to take his adopted parents with them.
Sam and Dean explain to Jesse that his parents may be hurt if they come along, so Jesse wants to say goodbye to them one last time. While the Winchesters wait downstairs, Jesse peaks in on his parent, then goes to his room and looks at a map of Australia. Suddenly, he disappears. The episode ends with the boys driving down the road, talking about parents and children. Jesse may be gone, but this probably isn't the last we've seen of him...