Billy starts his first day of high school, only to discover that nothing has changed: he’s still barely five feet tall, still the target of bullies (in this case, one Cameron Black), and although his interest in girls suddenly burgeons when he meets beautiful Blythe Forrest he remains unable to even talk to her coherently.

Not only that, but his first period history teacher, Mrs. Russet, treats him very oddly by making him stay after class and spouting sudden nonsense at him. Then a month or two into the school year, Billy turns fourteen and accidentally hits Cameron in the nose, causing him to bleed, as Cameron is trying to stuff him into a locker.

Mrs. Russet sees this, and rushes Billy off to a janitorial closet where, to his great surprise, they end up facing a dragon. They are barely able to escape the dragon without getting turned into a cinder by its lightning breath, and then Billy finds himself on a fantastical island called Powers Island. Mrs. Russet informs him that there is something odd about him and they need to test him to figure out what it is. Apparently he Glimmered when fighting Cameron, which is the magical equivalent of flexing your muscles, and he should not have been able to hit Cameron in any case.

He meets Vester (a fire Power), Tempus (an air Power), a water power who doesn’t matter because he’s only in the one scene, Ivy (a life Power), and Mrs. Eva Black (a death Power, and Cameron’s mother). We also learn that Mrs. Russet (whose first name is Lumilla) is an earth Power. They want to determine what Billy is, but in order to do so they have to kill him. He freaks out at this but is ensured that it is safe.

They do the deed, and crazy randomness happens. Billy finds himself underground with Mrs. Russet, Vester, Ivy, and Tempus (Mrs. Black and the water guy having teleported out as soon as trouble hit). Tempus is out of his head and spouting prophecy about some “him” who is coming, and Billy is mysteriously alive, although no one had time to resurrect him.

Mrs. Russet leads everyone back to the pinnacle of the tower on Powers Island and calls a meeting of the Council (all the most powerful Powers, who serve as a ruling body). She reveals that she thinks that Billy is the Messenger, a person out of prophecy, and when he gets on their Diamond Dias, the thing cracks down the middle and a spur of pure diamond shoots out of it. Billy and the lesser powers Vester, Ivy, and Tempus are sent to a magical waiting room filled with hot chocolate serving Fizzles (magical constructs) to wait the Council’s decision.

The Council unfortunately is divided, and Mrs. Black and the water councilor walk out. Both are Darksiders, while the rest are Dawnsiders (Darksiders think Powers should take over the world while Dawnsiders want to hide from the mundane world, and the two have been involved in several nasty magical wars in the past).

The most recent magical war was lead by a man named Wolfen, who shows up and swears allegiance to the Council and to Billy, shocking everyone. He then pops back out of existence. The Council decides that it will keep testing Billy to try and determine what his abilities are, and sends him back to school. He is surprised to find that he arrives just minutes after leaving.

Blythe Forrest starts seeking Billy out, to his great surprise and delight, but just as they are about to share their first walk to class together (how romantic!) he is summoned back to Powers Island for his first test.

Mrs. Russet administers the test, in which she strands him on an asteroid with little air and a giant rock scorpion monster. Apparently if he lives it means that he has power over earth. Of course, if he doesn’t have power over earth, he’s kind of screwed, so her testing approaches leave a little something to be desired.

Fortunately for Billy, he is rescued by a giant magical unicorn, which returns him to school. Mrs. Russet pulls him out of class all discombobulated, and rushes him off to Powers Island. There she goes to talk with the other Council members, so Vester and Tempus take him to the stadium to see a challenge for the fire councilor’s position.

The fire councilor is Fulgora, a beautiful woman who Vester is mad for. During the challenge, she is almost killed, but miraculously transforms into a dragon and kicks her challenger’s butt. As she is taken to the recovery area, panic takes over the arena as a bunch of zombies pop out of nowhere and start grabbing people.

Vester and Co. run to save Fulgora and teleport out onto a ledge in an active volcano, but a zombie follows them through. Billy barely escapes being knocked unconscious (if a zombie touches you, you end up either unconscious or dead), and is saved by Ivy, who Vester had told to meet up there if anything bad went down. Ivy reveals that the Council has been taken captive by Wolfen; apparently the Darksiders are again rising against the Dawnsiders, despite Wolfen’s apparently changed character. Mrs. Russet left a cryptic message with Ivy for Billy.

Fulgora regains consciousness, and runs off to do Councilor-things. Or something.

Billy figures out the message means he needs to go to Mrs. Russet’s classroom at school, so they all teleport over thataway and discover a talking ceramic frog that tells them they need to get to Powers Island. However, the frog’s recording capacity runs out before Mrs. Russet is able to tell them what it is they are supposed to do, and presumably she was too frustrated with the construct to re-record her message. That happens to me a lot, too.

In any case, they head to Powers Island only to discover the Accounting room (where everyone has to teleport into) is overrun with zombies who will not allow people to pass unless they are labeled as Darksiders by the Counter machines. Ivy sacrifices herself without a fight, Vester and Tempus go down fighting, and Billy is left unmolested since he is still undecided. However, Cameron Black teleports in unexpectedly, and Billy barely makes it into the elevator.

He heads to the Council room at the top, where he runs into Wolfen, who comes close to killing him until Billy escapes with the help of a snake Fizzle created by Vester that apparently stuck with him and locks himself in the hot chocolate waiting area. By making a huge mess, he causes the Fizzles who clean the area to teleport him away, just as Eva Black is coming through the door with Wolfen.

Billy finds himself in the care of a crazy old man named Rumpelstiltskin (Terry to his friends), who claims to be Mrs. Russet’s husband. He is obsessed with cleaning up the island, and advises Billy with the brilliant plan that he should just give himself up to the zombies. He then has a brief lucid moment, spouts off some nonsense prophecy, and transports Billy back up to the Accounting room via the power of earth.

Billy takes his advice and ends up captured and transported to Dark Isle (these guys really know how to name things). Wolfen and Eva Black take him out of his glass cage and transport him to the pinnacle of the island where they alternately threaten and try to convert him to their cause. He discovers to his horror that Blythe Forrest is a Darksider, which causes him to doubt everything he’s ever known.

Fortunately, the weird prophecy provided by Terry indicates that he has to pass through water, so he jumps off the cliff and falls into the sea where he is promptly swallowed by a whale and passes out when the air in the whale’s mouth runs out.

Billy comes to deep under the ocean in the control of Blue, a mysterious mermaid who tells him that she transformed his body to be able to withstand the deeps at the whale’s request. She makes a bargain with Billy to kick the Darksider’s butts if he gives her the White King’s sword.

Blue transports Billy back to Dark Isle where the basically destroys everything with the grandmother of all tidal waves, saving only Billy’s friends. Everyone except Mrs. Russet is doing alright; Mrs. Russet, however, is trapped in her memories by a black power called the Dread that traps a person in their greatest fears. With Fulgora’s help (she teleports in on her own), he is able to free Mrs. Russet and at the same time forges a much stronger relationship with her.

Billy is distraught at the destruction he caused until he realizes that—just kidding!—Blue actually saved everyone (Darksider and Dawnsider alike) except the zombies. Billy asks the Dawnsiders to be transported to Powers Island, and the Darksiders ask to remain on Dark Isle after the water washes away.

Back on Powers Island, the Dawnsiders start preparing for war, knowing that they have a time advantage thanks to the enchantment on the island.

They figure the only way to win against the Darksider’s superior numbers is to bottleneck them in the Accounting room. Except of course—surprise!—the Darksiders don’t feel bound by the rules and start popping out everywhere. As Wolfen and Mrs. Black wreak havoc in the Council chamber, Billy flies around with Tempus dropping rocks on people and observing the quick subjugation of the Dawnsider forces. Fortunately at the last minute Rumplestiltskin shows up and freaks out at the mess, unleashing his hordes of Fizzles to do battle which makes things start to look up. Sadly, the zombies then march out of the water, having shlepped over from where they got washed away by the tidal wave, and the battle turns once again.

Billy finally decides to be the damn Messenger and heads up to the Council chamber. There he finds bad things going down, but is able to make it to the Diamond Dias, pursued by a bloodthirsty Cameron. Cameron casts the Dread at him, but Billy ducks and it bounces off the diamond spur, hitting Cameron instead. The diamond spur breaks, and one of the shards becomes the sword that Billy has been seeking, which he plunges into the Diamond Dias and works some crazy magic to disable the Darksiders.

Wolfen drops dead, and Eva Black escapes using her beetle broach.

It turns out that Wolfen has been dead all along, but was being manipulated by Eva, which handily explains how he was able to lie to the Council about his allegiance, although sheds little light on why that seemed like a good idea. Everyone is happy with Billy until he tosses the sword into the ocean for Blue, at which point some people are not so happy with him.

It turns out that Billy is the messenger for the return of King Arthur, the White King who united the Powers way back in the day. Blue was once one of his councilors, so Billy just effectively returned Excalibur to the Lady in the Lake. There are other Arthurian weapons, however, that they think they might need to go find.

Billy returns to school, where for some unspecified reason he is now popular, and is happy to find that Blythe still wants to hang out with him.