Nina went back to her room to sleep.
In this world, most people went to bed early and rose with the dawn—the time after the sun set was dangerous, and the faint glow from the Creation of the World would lead to the most severe degree of distortion across the globe. Even with the protection of city lights, people had to face the night cautiously.
Unable to go out and gather, lacking many forms of entertainment, reading books at night wasn't as dangerous as reading at sea, but it could easily lead to mental exhaustion, auditory and visual hallucinations. Occasionally, it would even attract unwanted peering from the darkness. Therefore, considering everything, the safest method was to go to bed early and wait for the sun to rise the next day.
Duncan, however, did not feel the slightest bit sleepy.