Ten-year-old Emma is excited to explore her new home of San Francisco, but making new friends is difficult. That is, until she meets Julie.... well, she discovers her journal from 1977 in a local thirft shop and quickly becomes enraptured with a mystery unfolding in Julie's time.

Though half a century separates them, Emma and Julie are united by their shared home, their passion for the environment, and a missing blue guitar. As Julie investigates stolen artifacts and works to help animals after an oil spill, Emma sets to work uncovering Julie A.'s identity, documenting the whole process on video for her school project.

This new mystery graphic novel from American Girl and IDW weaves together two storylines, past and present, ending with a modern girl and a historical character joining forces to make a difference today.