What is the the conflict in chasing Vermeer and what characters were involved?

In "Chasing Vermeer" by Blue Balliett, the central conflict revolves around the mysterious theft of a valuable painting by the artist Johannes Vermeer. The protagonists, two sixth-graders named Calder and Petra, work together to solve the mystery and uncover the connection between the painting's theft and a series of clues tied to Vermeer’s work. As they delve into the art world, they encounter various characters including their teacher, who encourages their investigation, and other individuals with motives related to the painting. The story explores themes of art, friendship, and the importance of thinking critically.