A fantasy-loving boy learns to cope with loss by adjusting his ideas of what it means to be a hero and figuring out how to face a monster he can't slay: his grandfather's Alzheimer's disease.

When Archie's beloved grandpa is diagnosed with Alzheimer's disease, Archie desperately wants to slow the progression of his grandpa's memory loss. Using Grandpa's old journal entries as inspiration, he creates shared role-playing fantasies with epic quests for them to tackle together—allowing Grandpa to live in the present and stay in touch with his fading memories.

But as Grandpa's condition gradually worsens, Archie must come to terms with what's happening to his hero. The limits of the fantasies, revelations about Grandpa's past, and a school project about the future force Archie to grapple with what it truly means to live a life worth remembering.