In a cost-cutting move, Principal Greedyguts has replaced the school lunch lady with janitor Leo Louse. Faced with dishwater lemonade, sawdust soup and other revolting concoctions, Jacob decides that something must be done. With the help of Buford and his new next-door neighbor Mr. Dinglebat (an international spy), Jacob discovers Leo's secret dungeon kitchen, and he reveals the truth about the lunches to their parents. Greedyguts is forced to rehire Bella Bountiful, lunch lady extraordinaire, and Leo Louse is sent back to his lowly janitor's closet.

Jacob is tired of failing sour Pickle's daily country capitals quiz, so he does a little detective work, and he figures out her system for picking which countries to ask. As a result, he aces the quiz, and he becomes a hero to the entire student body. It all backfires, however, when he is chosen to be the geography expert on the school's "Scholars for Dollars" team. He's only got one night to memorize all the countries and capitals before the big competition!

Jacob is fed up with sharing his room with his brother, Noah. He decides to try a living space --- the attic of his home. He finds it too scary though and thanks to his siblings' taunts, worries about being pursued by a wrestler that goes after children. He learns that he has to face his fears head-on in order to overcome them.

It's school photo day, and Jacob wakes up with the nastiest cowlick that you've ever seen. Principal Greedyguts has promised dire punishments to those who don't look absolutely perfect for the photos, so Jacob has got to tame his hair, and quick! When tape and glue doesn't do the trick, Jacob and Buford turn to a gooey concoction of hair products& which turns the whole mess green! The barber can't help him, neither can the hairstylist, but Renee the chemistry whiz thinks that she can undo the damage.

Jacob becomes obsessed with solving the real-life mystery in his Malty McGuffin book; the mystery is supposed to lead to a real secret treasure. The only problem is that he is being followed by library ninjas intent on getting the book back. Jacob, Buford and Renee use their combined brainpower to decode the clues, solve the riddles, and find the location of the secret treasure... only to be scooped at the last minute by I.M. Greedyguts! Will the library ninjas turn the tables on their principal? Will Jacob return his library book on time?

The school science fair is fast approaching, and Jacob still hasn't come up with a project. To make matters worse, Mom and Dad have gone away on a trip, and the dreaded Auntie Good-For-You is babysitting Jacob and his siblings. Auntie won't let them do anything which isn't good for them, which means no fun allowed! When Jacob accidentally grows a huge, weird fungus in his closet (with the aid of Auntie's green health shake), he figures that his science project worries are over! If only he can keep it hidden from Auntie and prevent it form eating everything in the house as it grows, and grows, and grows.

It's his first day at a brand new school, and Jacob wants to look cool, so he borrows his brother Daniel's favorite skull T-shirt to wear. What he doesn't realize is that skull shirts are against the school rules, and before he knows what's happening, Principal Greedyguts has confiscated the shirt and locked it away in the school vault. Jacob's got to get that shirt back! Aided by an odd kid named Buford and a daredevil skateboarder named Renee, Jacob dares to enter the forbidden Staff Room of Doom! Together, they face Greedyguts' Indiana Jones-style booby traps, and they make a daring escape. Jacob gets the T-shirt back, and he makes two new best friends in the process!

When Jacob receives a Gummer Gormley form dad he decides this is just the lucky charm that his hapless hockey team needs to end its record-breaking losing streak. With the card in hand, all goes well, and the team is finally winning some games... until perfectly loathsome Leo Louse steals the card from Jacob's locker. Jake and Buford visit the aged Gummer Gormley to ask for another card, but he turns them down, reminding them that skill wins games, not luck. Back at the arena, Jacob pulls himself together, and he leads the team to a win, proving the old hockey legend's words to be true.

Jacob's grandpa is coming to visit, and that means it's time for one of Dad's special Sunday brunches. Jacob is entrusted with the all-important trip downtown to fetch the bagels. He takes this responsibility very seriously, but as soon as he leaves the house, everything starts going wrong. Eluding bullies, dodging vicious dogs, braving sudden snowstorms, and outwitting Principal Greedyguts. Will Jacob come out on top and deliver the bagels in time for brunch?

A new newspaper becomes an overnight success in Montreal, but Jacob is suspicious. The paper is poorly written gibberish, and yet all the grownups in town subscribing to it and are spending all their money on the useless products advertised in it. Jacob and Buford become paperboys to infiltrate the Daily Crown headquarters, coming face to face with its eccentric founder, Carl Fester King. Learning that the paper's ink does indeed contain a brainwashing chemical, Jacob uses King's own newspaper to reveal his con-game to the entire city.

Jacob discovers that he has a ghostly roommate named Claude LaToque, a former coureur de bois. A friendship quickly develops, but soon, Jacob learns that Claude is hiding a shameful secret about his past, which he doesn't want Jacob to know lest their friendship come to an end. As he tries to learn the truth, Jacob finds himself transported back in time to a lonely trading post on the night that the terrible event took place. Jacob's trust in Claude is not misplaced, and as he learns what really happened that fateful night, he also redeems the tarnished reputation of his ghostly friend.

The school superintendent has shut down the school's decrepit gymnasium, and the only way to get it reopened is to sell a record number of candy bars in the school fundraising drive. Jacob spearheads the effort, encouraging his fellow students to get out there and sell, sell, sell! When he hits the street, however, Jacob finds out that it's not so easy selling to complete strangers, especially when your last house is the haunted abode of a notorious mad scientist!

With the help of Intrepid the hamster, Jacob uncovers a plot by a group of little old ladies to cover Montreal in a gigantic tea cozy. They've been stealing all the wool that they can get their hands on for their secret project, including the bunny sweater that Jacob's grandmother has knit for him. Jacob foils their scheme, and he rescues the embarrassing sweater before it gets unraveled.