At the very beginning of the book we learn that Nick Fury of SHIELD has sent the Hulk into space to destroy some sentient satellite thingy and the Illuminati which consists of Reed Richards, Professor Xavier, Tony Stark, Black Bolt & Doctor Strange hijacked his space ship to send him to a world without intelligent life where he could hurt no one. Of course this freaks the Hulk out and he begins ripping his ship apart which alters his trajectory and diverts him straight into a wormhole.
After leaving the wormhole the Hulk’s space ship crash lands into a populated planet where he is immediately attacked by its inhabitants. Apparently the travel through the wormhole weakened the Hulk so he actually loses the fight and gets enslaved by the imperial servants of the planet and gets an obedience device installed in him.
Hulk is then sold and then thrown into the slave pits to fight monsters. When Hulk defeats the first monster he attacks the Red King, the villain and leader of the world’s empire — which begs the question as to why he a king instead of an emperor. The Red King dons a Robotech-like set of armor which supposedly makes him invincible, yet the Hulk is still able to cut him before he is cowed through his obedience disk.
Hulk gets teamed up with seven other gladiators and they bond over their victories and pledge loyalty to each other. As time goes on Hulk begins to get his strength back. With his renewed strength, Hulk and his team of gladiators defeat each group of monsters that they get thrown into the arena with. Fearing that the locals are beginning to see Hulk as the fulfillment of an old prophecy – one who will both save the world & destroy it – the Red King’s men throw Hulk into an arena with the one person they believe that he cannot defeat, the Silver Savage who is really the Silver Surfer who also has an obedience device.
In the fight that follows, Hulk smashes the Silver Surfer’s obedience disk which frees him and returns his power cosmic. With his power restored the Silver Surfer is able to free all of the slaves which begins a rebellion of former slaves & outcasts against the empire.
The Silver Surfer leaves the planet leaving Hulk there by his own request. With his new army of gladiators and former slaves Hulk defeats all enemies that the empire throws his way. When the Red King goes as far as bombing his own people to destroy the Hulk, his bodyguard named Caiera the Oldstrong who is nearly a match for the Hulk himself leaves the empire and joins Hulk’s crusade.
The Red King uses captured aliens who infest any life form the find and turn them into killing machines known as the “spikes” to hunt down and destroy Hulk’s army. Through the abilities of one of Hulk’s new allies, the Hulk finds a way to converse with the leaders of the spikes and makes them his ally.
The Hulk then brings the fight to the Red King and defeats him. The Hulk takes the role of King over the Empire and takes Caiera as his queen. He tries to bring peace between the the different factions of the empire and even plays with the thought of just escaping into the wilderness with the woman he loves before she tells him that he doesn’t need to run away and hide and that he has found his place in life. Caiera also tells him thatt she was pregnant with his child.
In celebration, some of the Hulk’s loyal citizens bring out his salvaged spacecraft to the center of the capitol city. When they do it begins emitting an alarm signaling that the core of the spaceship is compromised. Hulk tries to throw the spaceship out of range before it explodes but it is too late. Everyone in the capitol is killed instantly, and only a handful survive, including the Hulk’s fellow gladiators. The Hulk blames the humans for destroying his world, his queen and his unborn child and declares war on Earth and begins the journey back home.
This leads directly into World War Hulk.
Ok, I have to admit it; I actually saw the Planet Hulk cartoon before I read Planet Hulk, sacrilege right? (see the video below) So how did they differ, well the cartoon had much less depth and perhaps a happier storyline. But it’s the graphic novel we’re really interested in right now so let’s get into that.