Nightfall

The narrative shifts its focus to Siferra 89, an archaeologist from Saro University. Siferra is conducting an excavation on Beklimot, the remote site of the oldest known civilization on Kalgash. Her work, however, is threatened by a devastating sandstorm, which not only endangers her equipment and her team but also the very ruins they are excavating.

Siferra tries to secure as much of the location as possible before taking shelter with her team below a nearby cliff. The storm eventually hits, and it terrifies Siferra so much that she bursts into tears. She worries that the ancient city could be lost due to her negligence.

To everyone’s surprise, the storm clears, revealing that the ruins have been spared from damage. However, a nearby site called the Hill of Thombo is revealed to have been split apart by the storm, revealing a series of secret cities buried underneath. Siferra orders the team to excavate the hill immediately.

Kelaritan, Cubello, and Sheerin interview Harrim 682 in his hospital room. Sheerin asks Harrim about his recovery, noting that Harrim is free to go home anytime. Harrim seems hesitant to leave his room, fearing that he will be engulfed by total darkness once again. Kelaritan notes that while Harrim seems agoraphobic now, he had been claustrophobic in the previous weeks.

When Sheerin asks him to recount his experience riding the Tunnel of Mystery, Harrim shares how he had won his ride ticket in a lottery, which he immediately redeemed with his family. Although he had never experienced total darkness before, he had been excited to go because everyone else he knew seemed eager to try it. During the ride, Harrim had experienced intense claustrophobia.

Kelaritan notes that among the survivors, Harrim seems to have emerged with relatively minimal psychological scarring. Other survivors refused to enter enclosed spaces after visiting the Tunnel, usually sleeping out in the open and becoming violent when forced to go indoors. Kelaritan notes that Harrim is in the second phase of symptoms, believing that it is brighter indoors than it is outside. Kelaritan offers to take Sheerin to visit the Tunnel after lunch.

The perspective shifts to an astronomer named Beenay 25, who is preparing for an appointment with his younger colleagues, Yimot 70 and Faro 24, at the Saro University Observatory. Beenay’s romantic partner, Raissta 717, complains that she cleared her schedule to spend time with him, so Beenay settles for a compromise with her, promising to return as soon as his appointment is finished.

At Raissta’s request, Beenay explains that he is studying the Universal Law of Gravitation, which he has possibly disproved. To investigate further, he has tasked Yimot and Faro with conducting an independent experiment to see if they can replicate his findings.

Siferra haphazardly tries to widen the new opening on the Hill of Thombo. She deduces that a fire must have burned down the uppermost layer of settlement, which had been built on the ruins of an even older city. She believes that if they can continue to excavate the hill, they can uncover even more layers of civilization. Her hypothesis proves correct as they expose a third burnt city underneath. She suggests that there may be as many as eight layers under the hill. Siferra allows her colleague, Balik 338, to take some photos of their findings, all the while marveling at the implications of the discovery on her career.

After a day of interviews with the Tunnel survivors, Sheerin dreads entering the Tunnel of Mystery himself. He reassures himself with the knowledge that the survivors he met were merely outliers. He meets with Kelaritan, Cubello, and Varitta 312, an engineer who helped design the Tunnel attraction.

On the way to the Jonglor Centennial Exposition, Cubello reveals that Harrim’s experience bolstered interest in the ride. People were curious to see if it was as terrifying as they had heard. Their interest only intensified when visitors started dying. The city only decided to shut the ride down for insurance purposes; their growing concern is the mounting costs of compensation for those who have been harmed. Kelaritan notices Sheerin’s hostility and suggests holding back on riding the Tunnel, but Sheerin insists. The group arrives at the Exposition and immediately proceeds to the Tunnel of Mystery. Before they enter, Cubello asks Sheerin to sign a release form. Varitta gives Sheerin an abort switch to activate the ride lights.

Sheerin enters the ride and continuously reassures himself with rational explanations for Darkness Syndrome. As he goes deeper into the ride, however, he starts experiencing claustrophobia and anxiety. He resists aborting for as long as he can and even throws the switch away. He tries to calm himself down, despite having lost all sense of time. He is relieved when the ride finally ends. He tries to downplay the ride’s psychological effects but is unable to hold back his emotions when he urges Cubello to permanently close the ride.

Beenay arrives at the observatory, where he bumps into Theremon 762, a friend and journalist for the Saro City Chronicle. Theremon wants Beenay to offer a counterpoint to an alarmist screed by Mondior 71, the leader of a religious group called the Apostles of Flame. Beenay wants to help but remembers his promise to Raissta. Theremon offers to meet the following morning.

Beenay enters the observatory and reverently stops before the display containing the Theory of Universal Gravitation manuscript, which was developed by Observatory Director Athor 77 and is described as the foundation for all modern astronomical research. Beenay rushes up to meet Faro and Yimot, who deduce that the task they’ve been assigned involves gravitational theory. Beenay reviews their calculations and finds that their deviations match the ones he had reached on his own. He realizes the dilemma of announcing that he has disproved his mentor’s greatest work. Upset, he denies that the task has any real-world implications and leaves.

Beenay calls up Theremon and asks to meet that evening instead. He doesn’t want Theremon to break the news to the public, but he needs to share his dilemma with a friend. He goes home and seeks comfort in Raissta’s embrace.

That evening, Theremon and Beenay meet at a bar. Beenay explains Athor’s Theory of Universal Gravitation, which Theremon has a passing familiarity with but does not truly understand. According to the theory, the movements of all the bodies in the universe are influenced by each body’s mass and proximity. This theory allows astronomers like Beenay to calculate Kalgash’s orbital movement amid neighboring bodies. However, Beenay has found discrepancies between the theoretical and the actual orbital positions of Kalgash in relation to its suns, which has led him to conclude that Athor’s theory is wrong.

Theremon understands that Beenay is worried about how this discovery will affect Athor. Beenay looks up to his mentor as a father figure but knows it would go against his professional conscience to suppress his own research. Theremon suggests that if Athor values scientific truth as much as Beenay does, he won’t mind having his own work disproved. He reminds Beenay that science is constantly revising previously understood truths with new discoveries. Alternately, Theremon suggests that if Athor’s theory holds true, it would imply the existence of an unknown factor influencing Kalgash’s orbit. Beenay opens himself to that possibility but points out that it is difficult to prove anything based on pure conjecture the way the Apostles of Flame usually do. He promises to tell Athor the truth.

In return for listening to him, Beenay agrees to give Theremon the statement he wanted. Theremon quotes to him the doomsday prediction made by the Apostles of Flame leader Mondior 71, corresponding to the Apostles’ general belief that the world has been destroyed several times in the past. The Apostles preach that the gods judge mankind every 2,049 years, destroying the world with divine flames called Stars, which are different from Kalgash’s six suns. The gods then spare the holiest survivors, urging them to rebuild civilization according to their moral value system. Mondior predicts that the next judgment will come in 14 months’ time. Mondior has stated that his prediction can be verified scientifically through the Theory of Universal Gravitation, and this is why Theremon wants a statement from Beenay: If Universal Gravitation is untrue, then Mondior’s proof will be invalidated.