The Tuttle family is having a fun day together at the carnival when Ethan and Emily notice a particularly exciting item at the prize counter: a telescope. It’s the perfect one to see Junie’s Comet, which will cross the sky that night. But when Ethan and Emily make their way over to check the telescope’s ticket price, the pair notice some extreme increases in the tickets required for each prize at the counter. In the midst of their despair and confusion, bumbling Copernicus slides up to the stand with an absurd amount of tickets and effortlessly purchases whatever he wants.

This is when the twins discover Karinne, wielding a wheelbarrow of tickets and handing them out to her potential constituents as candidate for Kids’ Club President. Karinne reveals that her uncle, who runs the carnival, had put her in charge of printing the tickets for each carnival game. In an effort to bribe her voters, Karinne began printing extra tickets to hand out to the neighborhood kids.

When Ethan and Emily inform Grandma Gabby about the ticket-printing fiasco, she whisks them away on an adventure to learn about the dangers and causes of inflation.

The gang’s first destination is Stockholm, Sweden in 1976. Gabby and the kids pick up the legendary Milton Friedman, just before he’s to win the Nobel Prize in Economics.

With Friedman in tow, Grandma Gabby then takes the twins to Ancient Rome, particularly to where the government minted their coins. The gang watches as these early individuals start to fall prey to inflation, making their coins with less and less precious metals and in higher volumes. Milton Friedman explains that the Inflation Monster–which the twins can see with special goggles–always starts out this way; a government begins creating more money than is responsible, devaluing the currency and spreading the monster’s effects into everyone’s financial lives.

The group’s next stop is a brief visit to Washington D.C. in 1925. They visit the Federal Reserve, the American institution responsible for controlling the value of the nation’s currency. Ethan and Emily learn that, while the Inflation Monster grows every day, its effects are so gradual that they often go unseen before it’s too late.

In one final stop before they return to the carnival, Gabby, Milton Friedman, and the twins visit Harare, Zimbabwe in the year 2008. Grandma Gabby introduces the group to her friend, Tatenda, who explains that Zimbabwe is facing a devastating financial crisis. Food prices rise daily, leaving people hungry and struggling. All of this began when the Zimbabwe Reserve Bank incited hyperinflation by overproducing currency, to the point where a single U.S. Dollar equaled 1 trillion Zimbabwean dollars in value. “Inflation makes poor people poorer,” Tatenda teaches the kids. Now the twins know what they need to do: they need to stop Karinne from printing excess tickets.

After getting Milton Friedman some stylish new skinny jeans, Gabby, Ethan, and Emily drop him back off to receive his Nobel Prize and race back to the carnival to stop Karinne. The twins try to teach her about inflation, but she doesn’t listen. Just as Karinne is about to restart the printer to do additional damage, Derek the raccoon manages to put the special goggles on Karinne so she too can see the Inflation Monster. After seeing the devastating reach of the Inflation Monster in the carnival, she experiences a change of heart.

When Karinne explains her mistake to her uncle, he tasks her with removing the extra tickets in order to normalize prices. He gives the twins the prized telescope they would’ve been able to afford, had the Inflation Monster not had its field day. The family’s night is saved, Karinne gets to work burning the excess tickets, and the twins marvel at Junie’s Comet together.