The plot focuses on a three inch tall boy who runs away from humans to live with mice, only to discover that the mice are regularly massacred by rats every seven years. The mice, however, cannot anticipate the attacks because they can't count past three. As a result, Hercules must teach them to count in base four.... The book contains a mathematical appendix to teach readers how to count correctly in base 4 (Hercules doesn't do it well in the text); an appendix to the appendix that discusses base two; and an appendix to the appendix to the appendix, which teaches kids to count in hexadecimals.

Hercules found that his head was pounding. He took a deep breath to settle his shaking hands. Then he ripped a piece of paper into ten pieces and laid them down. "One, two, three," he counted in mouse-squeak. Then he took the fourth piece. "Humans have a number for this one, too," he said. "We call it four" He took up the next. "Five"

Quangster was staring at him, shaking his head. "I almost understand," he said, " but I feel like there's a cloud before my eyes."

"It's okay," Hercules said. "I'll try something else." He laid out three pieces of paper, then three more below them, and then three more beneath them. "Look here," he said. "One, two three, as you know. The rest are lak right? But you can see that the lak are broken into groups of three. He paused to make sure Quanster was following. Quangster's brow was furrowed. His paw curled around his tail as it always did when he was thinking hard.

"Let's call this second row lak-one," Hercules went on. "We'll call this number one-one: the first lak number. This number is one-two, the second lak number. And this, one-three. those are the first three number after three."

Quangster looked, and squinted, and though, and then with super-rodent effort, pointed to the third row. "This is lak-two?" he guessed. "And we call the numbers two-one, two-two, and two-three?"

Hercules stood up and did a little dance. "Quangster," he marveled, "you must be the first mouse ever to count past lak!"