Monsieur Perdu calls himself a literary apothecary. From his floating bookstore in a barge on the Seine, he prescribes novels for the hardships of life. Using his intuitive feel for the exact book a reader needs, Perdu mends broken hearts and souls. The only person he can't seem to heal through literature is himself; he's still haunted by heartbreak after his great love disappeared. She left him with only a letter, which he has never opened. After Perdu is finally tempted to read the letter, he hauls anchor and departs on a mission to the south of France, hoping to make peace with his loss and discover the end of the story.