'Old Saint Paul's: A Tale of the Plague and the Fire', written by William Harrison Ainsworth, is a historical romance novel that takes place during the Great Plague of London and the Great Fire of London. The story follows grocer Stephen Bloundel's life and his daughter Amabel's love triangle with his apprentice, Leonard Holt, and Maurice Wyvil. As the plague devastates London, St. Paul's Cathedral becomes a shelter for the sick, and the characters' lives intertwine in unexpected ways. The novel offers a vivid portrayal of the historical events that shaped London.