Sixth @-@ graders Calder Pillay , who enjoy puzzles and pentominoes , and Petra Andalee , who aspire to be a writer , are classmates at the Middle School in Hyde Park , Chicago . Their young teacher , Ms. Hussey , is very interested in art and teach them in a creative way . Through her pressing questions , they discover the artist Johannes Vermeer and his paintings , especially A Lady Writing and The Geographer . Petra also find a used book called Lo ! , written by Charles Fort , at the local Powell 's Books , owned by a man named Mr. Watch . They also meet an elderly neighbor , Mrs. Sharpe , who is also a fan of Vermeer and Fort . Calder receive letters from his best friend Tommy Segovia , who is currently living in New York City with a new stepfather .