During the night, Grumpy and Spike fight it out while the Marshalls sleep peacefully and comfortably in their cave. As they sleep, a thin strand of sand pours out of a gourd into a bowl below. Meanwhile, a band of Sleestak roam the jungle through the darkness to arrive at one of the pylons. A Sleestak approaches the humming structure cautiously, then turns the key and climbs inside. The Sleestak wanders over to the matrix table and carefully plucks out a crystal with his claw. The result of the action is made very clear when we see that the fast-moving moon in the sky comes to a halt.

The Marshalls are awakened when the bowl fills with enough sand to tip the see-saw it rests upon, causing a loud clacking noise. Holly is ecstatic that her "alarm clock" worked, but since the sun hasn't yet risen, Will grumbles that it doesn't keep very good time. Holly claims that she set it for 8 hours, and Dad confirms with his wristwatch that they had indeed slept for that long. The whole family steps outside to check the moons in the sky, where they immediately notice that "speedy" (the center moon) is not moving. (The story editor and special effects staff failed to notice -- or care -- that they keep recycling views of the three moons lined up exactly side by side. According to "The Pylon Express" episode, this only happens every 3 to 4 years; the next time it does, the Marshalls can use a time doorway that lies with in a special pylon to return to their own time and world). Dad notes to his kids that the last time something similar happened was when a crystal blew out in the Clock Pylon, so he decides that they had better go check it out. He asks his son to stay behind at the cave, just in case the Sleestak "decide to move in". While checking on the family's supply of crystals, Holly accidentally touches a red and yellow one to create a bright light; after separating the glowing two, she reports that they have a few of each color. (The story editors apparently didn't care about consistent use of crystal colors; green and yellow cause a bright light [Downstream], while red and yellow cause an explosion [The Search].) Dad simply asks her to fetch one of each color, and the two then make their way out of the cave.

Holly and Dad stroll quietly through the jungle and arrive at the pylon to find its door closed. Dad decides to open it up, and after he turns the key they both step inside. Dad quickly notices that a crystal is missing from the matrix, and suspects the Sleestak did it in a plot to achieve eternal darkness. He explains to his daughter that he will try replacing the stolen crystal with one that they brought along, one color at a time; he asks Holly to meanwhile look outside, and tell him when the smallest moon is set back into motion. The Sleestak lurk behind jungle foliage nearby, while Holly reports to Dad that neither the blue or green crystals worked. When the yellow crystal fails to work, Dad reasons that it must be the red, but before he can try it, Holly is captured by the Sleestak. Dad drives off the Sleestak for the moment by creating a bright light with the crystals, and orders his daughter to retreat with him to their cave.

While Sleestak roam the Lost City plaza, Enik arrives at the Library of Skulls. He is granted entry by the Sleestak guards to speak with he Sleestak Council within. Through a channel of telepathy provided by the sacred smoke, the Sleestak Leader addresses his "dwarf brother of strange ways", asking what he seeks in the Library. Enik replies that he has come to seek the reason for the Sleestaks' making the night go on forever. When the Sleestak Leader prompts the dwarf Altrusian for his purpose in obtaining such information, Enik innocently proclaims that he desires such information so that he may spread the Council's wisdom throughout the tunnels. The Sleestak Leader accepts the dwarf's reason, and begins to explain the Council's motive. The Leader explains that the Council asked the skulls to show them the way to eternal night; without the sun to drive them back into their tunnels, they will be free to hunt the sacred Altrusian Moth in great numbers. Within 1000 hours, the Leader claims, they will have 1000 fertile eggs in the Egg Cave; they will once again become total rulers of the Land. In a voice of undetected sarcasm, Enik praises the Council's brilliant reasoning and asks to know how the miracle was performed. When the Leader restricts any further knowledge for fear that the Altrusian would take power, Enik finds it humorous that the Council would believe that he would desire to rule the Sleestaks' miserable collection of tunnels. After the Leader warns him not to mock the Council, Enik returns by warning that the plan sends them all headlong into extinction. The Council does not understand the concept of extinction, so Enik tries explaining it to them. He argues that the Sleestaks' abuse of their newly acquired secret of the Clock Pylon will mean the end of the Altrusian race, but the Leader interprets Enik's forewarning as a plot to trick the Council. Enik demands that they consult the skulls to find their fate, then offers to do it himself, addressing a skull without the Council's permission. The Leader is deeply offended by the Altrusian's unauthorized action; he declares that Enik is forbidden to consult the skulls directly, and permanently bars the dwarf from the Library. Sleestak guards are called upon to haul the Altrusian away.

While Will waits back at their cave, he is repeatedly molested by large black moths. All of a sudden Dad and Holly come rushing up the steps; Dad urgently calls upon his son to start a fire on the porch, since the jungle is infested with Sleestak. Will asks Dad about trying to fix the pylon, but he informs his son that none of the colors seemed to work. Holly notices large moths lying burnt up around their campfire; Dad informs her that they are Sleestak moths. The cold is setting in, so Holly goes to get her coat. When Will brings the firewood out to the porch to start the bonfire, he announces that they are too late -- Sleestak are already arriving. To his surprise however, they have escorted Enik to High Bluff.

While Will goes out to add wood to the porch fire, Dad discusses with Enik the purpose of his visit. The Altrusian has come to request that Dad go to the Library of Skulls to learn the fate of the Sleestak from the skulls. Dad does not understand why Enik cannot explain to the Sleestak that the cold is killing their moths, and that therefore the Sleestaks' eggs will die also. The Altrusian explains that he is barred from the Library, since the Sleestak believe that his access to the knowledge would give him the power to command them. Dad points out the very real danger of the Sleestak "ripping his head off" when he visits the Library, but Enik assures him that he will be under the protection of Altrusian Grace. He who helps a Sleestak is granted the permission to ask one question in the Library of Skulls; while journeying to the Library, that person is granted protection from harm, and that protection is called Altrusian Grace. It is a tradition dating back 1000 years, back to the time from which Enik came. Dad realizes that he must have earned the right to such protection when he previously fixed the Clock Pylon; Enik adds that the Sleestak's learning of the pylon is what gave rise to the crisis that they now confront. Although Enik notes that he is allowed to be Dad's counselor in the Library, Dad still has a bad feeling that the Altrusian is hiding something. When Will asks Enik how can they be sure the ancient tradition still holds, the Altrusian simply replies, "how much wood do you have left?"

As Dad fastens on his backpack over his flannel coat, he is still not confident about Enik's plan. Enik leads Dad to the Sleestak guards waiting in the jungle, and telepathically informs the Sleestak that Dad claims Altrusian Grace. Luckily, the Sleestak allow them to pass freely; the granting of protection is still the custom. After walking through the jungle for a ways past rows of Sleestak, Dad stops to tell Enik that he heard the Altrusian in his mind. Enik informs him that his previous exposure to the sacred smoke in the Library leaves him with residual ability to read others' telepathic conversations. Dad asks Enik if the Sleestak can read can read his thoughts; Enik sternly replies that they could never penetrate the Altrusian mind and appears offended that Dad would ever believe it was possible.

Back at High Bluff, Will and Holly sit around the porch fire; Holly notices that the number of moths flying around has decreased. When Dopey comes around shivering and crying, Holly's heart goes out to the little brontosaur; Will, however, reminds his sister that poor little Dopey isn't the only one in trouble. (Since the water in the swamp would retain its much of its heat for weeks, Dopey must really be stupid to be wandering out in the jungle.) Down in the Lost City, Dad and Enik arrive at the Library, where the Sleestak Council informs the Altrusian that he is forbidden to enter. Enik announces to the Council that Dad has come under Altrusian Grace; he will be Dad's counselor and perform the "ritual of the book". Enik formally addresses the Index Skull to gain permission for Dad to ask a two-part question. The Altrusian counselor prompts Dad to ask the Skull of the Sleestaks' future, and though Dad is confused and reluctant, he follows Enik's wishes. When Dad asks the Skull of the Sleestaks' fate should it stay eternal night, the mist called forth from the urns holds no vision. Dad is perplexed at why they saw no image, whereupon his counselor interprets the void as signifying that the Sleestak would have no future. The Leader of the Council considers the question to be of no consequence, and impatiently declares that Dad's grace has been exhausted. Luckily, Enik recalls that permission for a second part was granted, so he urges Dad to hurry in asking where the second Clock Pylon is located. When Dad reluctantly does so, all they see is brief glance through the mist of Sleestak-guarded jungle pylon. The Sleestak Leader declares that the Altrusian dwarf has betrayed the Council, but Enik and Dad are saved from capture when the Index Skull upholds the Grace's guaranteed safe passage. The Leader of the Council heeds to the Index Skull's ruling, but warns Enik and Dad: "go from our site; return here and you will DIE. We have spoken."

The Sleestak await at the edge of the jungle near High Bluff; the porch fire begins to wane, and the Marshall's supply of firewood has been exhausted, so Will goes back into the cave to start breaking up their bed frames. Out in the jungle, after Dad and Enik are set on their own by the escorting Sleestak guard, Dad confronts Enik on why the Altrusian did not trust him in the Library. Enik explains to his human friend that he had to keep his plan secret, for if he would have told Dad, the Sleestak Council could have read his mind. Enik feels his plan came to naught, since the glimpse of the Clock Pylon did not yield much; Dad, however, notes that he has mapped most of the pylons' locations and suggests that they simply look for a jungle pylon guarded by three Sleestak. Enik is impressed by Dad's approach, considering the logic strange but effective.

After a brief while, the two locate the guarded pylon. When Dad points out that he will need a diversion to enter and repair the pylon, Enik reluctantly offers to feign a Sleestak Leader's voice to call away the guards for a moment. Dad sneaks around to the side while Enik hisses out to the Sleestak; Dad enters the pylon and gets to work trying out different crystals from a pouch he brought. The Sleestak soon discover that the Altrusian dwarf deceived them, so Enik telepathically calls out for Dad to hurry. Enik gets ensnared in the Sleestak guards' net, but Dad finds the proper crystal color just in the nick of time. The small, central moon once again races across the sky, and quickly the sun shoots above the horizon, forcing Enik's captors to retreat. Will and Holly are saved at the last minute as well; sunlight floods the bluff face, forcing Sleestak climbing up the steps to flee. The kids share a joyous hug in relief. After Dad helps Enik free himself from the net, the Altrusian thanks his human friend.

Will and Holly find their father while he heads back through the jungle to their cave. Dad assures Will that ordeal is really over and holds up the Clock Pylons' keys which he removed to ensure the family's safety.