Marco Gonzalez is a die-hard fan of The Ooze, a comic book villain with the power to sludge his enemies. During his first visit to HorrorLand, he comes across Chiller House and finds a solitary copy of "The Wizard of Ooze" and brings it home with him. He is told by Jonathan Chiller to pay him during his next visit.
After paying a visit to a comic convention, things start getting pretty weird for him. The Ooze (thought to be a man in a costume at first) follows Marco wherever he goes, and The Fabulous Flame (Sammy) starts showing up in random places, and even swipes the book from Marco.
Marco finds a section in the book with instructions that claim to give you superpowers. They worked, but only for 10 seconds. Eventually, Marco teams up with The Ooze to retrieve the book, but the short time span of his powers made The Fabulous Flame nearly impossible to defeat. His brother, Zeke, appears and reveals to Marco that he needs words from a special bookmark to make his special abilities last. Zeke defeats the two supervillains. After his adventures, Marco keeps the book safe behind a loose panel in his wardrobe. He tries to get the bookmark, but Zeke stops him, making promise not to search for it ever again.
Marco is then taken back to Horrorland after touching the glowing Horror Jonathan Chiller had given him earlier. Marco and a bunch of other kids, who had also brought souvenirs from Chiller House, stand in the shop confused. Chiller arrives and asks them to play a deadly game where they have to find the little Horrors (that transported them to his shop) so they can go back home. He says Hunters will start hunting them down the next day. He gives each one of them a Helper Card in order to find their Helpers, who are meant to help them find the hidden horrors.
The kids leave and split into groups: Ray and Sam, Andy and Meg, and Marco and Jessica. Sam and Ray soon find Ray's helper, who leads them to a joke red box. After their unpleasant encounter with Chef Belcher, they find Marco and Jessica and discover that the arrows used by the Hunters are real. Then they run into Andy and Meg and continue their quest. When they find Madame Doom, Andy walks into her tent and gets hit with an arrow. The kids stare in horror at the arrow lodged in his back, but Andy reveals that he's still alive and that the arrow was a fake. Turns out this was all a ruse by Madame Doom to make the game a little more "frightening."
Madame Doom reveals that the Helpers are actually the Hunters coming to get them. They flee and soon find out that Chiller is playing all the Hunters as they watch him disguise himself through a window. He tells them the game isn't over yet, but they can't take it much longer. Chiller tells them that the whole reason behind this game is because he never had any friends as a kid, so he created his own (the costumes). He was also desperate to prove himself a good hunter to refute his father's doubts. The children formulate a plan to put an end to this madness. They put on the disguises and tell Chiller that they're about to leave him, breaking their friendship apart. Chiller pleads with the children to take off the costumes, not wanting to be lonely again. He frantically gives the kids some plastic Horrors, which transports them back home safely.
Marco is a twelve year-old who acts mature and serious (everyone tells him that) and has a penchant for superheroes and comic books. He takes any and every scenario and talks about it in the context of a comic book.
Marco is tall and dark and serious looking, with a slender, serious face, black hair and dark eyes.