Who is your invisible neighbor? When Mrs. Johnson gives her fourth grade class this new riddle to solve, Isabelle can’t wait to take on the challenge. She’s a smart, curious girl who loves competition and hopes to be a veterinarian someday. But this riddle is the most difficult one she’s ever had to solve. Before she can unravel the mystery, Isabelle will need a few more clues. Join her on the journey as she meets a stranger, takes a surprise field trip, and hears a most unusual secret. Along the way, Isabelle learns to see things she’s never seen before.