It's Halloween night in Spooksville, and the gang goes to a party thrown by this guy Bryce. He swears that he lives alone, and while they don't necessarily believe it, they do notice that everything in the house seems to belong to him and that there's only one bedroom out of three that anyone uses. Bryce and Sally bot go as vampires, Adam wears a sheet to be a ghost, Watch goes as Sherlock Holmes, and Cindy is a fairy princess.
After talking about the witch, they agree to go to Ann Templeton's house. She gives them the option of choosing trick or treat. Adam and Bryce want Mars bars, which she gives them. Watch wants better glasses because he has problems seeing, and he gets new glasses. Sally refuses to make a decision, but Cindy hesitantly asks for advice. Ann warns her that she may find herself in a dangerous place by the end of the night.
While out wandering around town, they come across Dead Lane. There's apparently only one house on it at the very end, and people tend to go missing every year on Halloween. When they go to check things out, they see a flame inside a jack o'lantern rise in the air and float off on its own. They then hear someone screaming in fear inside, so unlike me, who would run away quickly, they decide to investigate.
They find a big picture of the house as it once looked with a kid dressed as a magician standing outside with a sign saying Marvin the Magnificent. They keep investigating, go throw a passageway, and find themselves in the basement. Sally and Bryce are suddenly thirsty, and Adam feels dizzy. The passageway moves from the basement and suddenly opens onto a large carnival.
A strongman instantly approaches them and recognizes them as newcomers. He says that his people know how to deal with creatures like Bryce and Sally and makes some more weird comments before wandering away. Watch suddenly starts smoking from a real pipe and develops a British accent when he leads them to a fortune telling booth. The fortune teller has two heads: one nice and one not so nice. The fortunes they give relates to Holmes and not Watch.
Watch keeps pressing them and learns that they were once just one girl from their hometown. Everyone who accidentally finds the carnival eventually becomes their costumes. They wander around town and find cowboys and other people living out their costumes. Watch then realizes that Sally and Bryce are both becoming real vampires.
This leads them to the magic show, which is some big deal. Marvin pulls a "volunteer" from the audience. The guy, who is dressed as a gladiator, starts crying, and a guy dressed like Wild Bill has to force him on stage and into a box by gun point. Marvin starts sawing through the guy's body and real blood seeps onto the stage, which makes Bryce and Sally lick their lips. Watch makes a big scene and demands that Marvin saw Adam in half instead. Since he's now become a ghost, the trick won't work. Marvin is so impressed, however, that he demands they join him for dinner in his fancy mansion.
They all go by horse and carriage to his mansion, and Cindy agrees to sit with him. It turns out that Ann actually told her that she was the only one who could save her group that night. When she raises her wand, which was part of her costume, Marvin gets worried and tells her that he's the Master and the only one who can control anything in this world.
When they get to his house, he separates everyone and Watch winds up in the dungeon. Over dinner with Cindy, he reveals that he knew Ann's grandmother when she was the town witch. When he went to her house on Halloween night, she gave him a book of spells. He later got sick and was near death when he read a spell, which sent him to this new world. Marvin also reveals that he's now trapped there and wishes he could go home to see his parents. Cindy offers to help but in a way that insinuates he doesn't have very much power. He then announces that if she doesn't help, he'll do unspeakable things to her friends.
Down in the dungeon, Watch and the gang are trapped. Adam walks through the cell door in his ghostly form and tracks down Cindy, who uses her magic wand to break the lock. The fortune telling duo shows up and hells them escape through the maze of the mansion. Marvin shows up just as they find a way back home.
Watch finally tells him the truth: there is a ghost in his old home, and it's his ghost. When he did the spell, he trapped his soul in this weird spot between life and death and his real body died. They convince him to go home and make peace with this spirit before moving on. Then, they all go through the doorway.
The epilogue lets us know that everyone comes home in the same form they were originally, including everyone trapped in that world in the past. They run into the two headed fortune teller and discover that she always had two heads. She lets them know that their futures now look bright.
*Last year, Ann apparently fed a neighborhood kid to the crocodiles in her moat because he planned to TP her house. Is it wrong that I like her?
*Ann demands that Watch do a trick for her first, so he uses the laser beam gun from the earlier book to fry one of her crocks. When she gives him his new glasses, she makes him hand over the gun first.
*A lot of people hide during Halloween because real werewolf went door to door the year before and ate a bunch of people. Watch claims he just got fur on their furniture.
*The strongman wears black shorts and black boots and has green skin. I wonder if this was some type of allusion to the Hunk?
*Sally and Bryce keep trying to eat people and suck their blood. Watch gets so freaked out that he keeps running away from them. Bryce suggests they try it just once before going home, but Sally points out that they probably wouldn't want to be human and know the taste of blood.