In Chapter 5, Doon Harrow explores Ember’s underground tunnels with growing urgency, determined to understand the city’s failing systems. Meanwhile, Lina Mayfleet stumbles upon a mysterious, torn piece of paper that could hold the key to Ember’s salvation. As the two teens follow separate threads of discovery, the fragile hope of escape begins to flicker to life—if they can decipher the clues before time runs out.