The Planiverse Computer Contact with a Two-Dimensional World
By A. K. Dewdney

Yendred, which is how the group referred to YNDRD, shows much of how things might operate in such a world. Yendred first appears to be merely a glitch in the 2DWORLD system, a five letter word, not in the dictionary for the program, spoken by a FEC. While this greatly worries Alice Little, Dewdney's course assistant, the class reaches the conclusion that it was most likely just a mistake caused by a misreading of bits because the FEC soon continues to behave normally. However, YNDRD appears on the console a second day, and it becomes apparent that he is not a mistake, but something beyond what was expected. Yendred begins to talk with the students, understanding and using English in forms other than previously programmed for FECs. Although Yendred at first appears like a FEC, he begins to morph on screen from the triangular two armed FEC into a four armed being with a much more complicated body anatomy. The 2DWORLD simulation screen also becomes more detailed as the students begin to see Arde, Yendred's world. Soon, every time the class begins 2DWORLD, they no longer work with the FECs, but instead speak with and follow Yendred as he goes through his world.

During the first few week of contact, the class learns about Yendred's environment. They explore his underground house as well as follow Yendred and his father on a fishing trip on fiddib har, the sea by his house. The house as well as the fishing trip really begin to explain how things operate in this two dimensional world. This is when the class begins to really think about Arde differently from Earth. Although many things are similar, the absence of a third dimension really changes things that seem so common on Earth. For example, the fishing boat only needs to travel in two dimensions and cannot turn, therefore it has no real front or back.

The second week, Yendred leaves his home to travel east. Eavesdropping on Yendred's conversation, the class learns that he is heading towards Vanizla, in search of something. Then, another difference between Earth and Arde is discovered. When Yendred first crosses paths with another Ardean, Tssil, one of them must lie down on the ground while the other walks over them in order to continue in their original directions since they cannot merely pass by each other. After parting with Tssil, Yendred explains that they are, or were, in a certain relationship, but that instead of the possibility of marriage, he has decided to go towards Vanizla. Once Yendred arrives in Is Felbt, a city en route to Vanizla, a traffic system is implemented which involves Westbound Ardeans walking into a covered pit allowing the Eastbound Ardeans to cross over, and then vice versa. Besides walking, Yendred also travels by balloon, a rocket, and a train.

While in Is Felbt, much of the technology on Arde is explained to the computer science class on earth. At this point though, the class has begun meeting in the lab at night in an attempt to stay away from a repeat of a story in a tabloid about the discovery of a 2DWORLD. The head of the computer science department tells Dewdney to stop whatever it is that he is doing. Therefore, the entire class now has a greater sense of secrecy about the work that they are doing. But, they cannot merely stop exploring Yendred's world. Especially not as they learn about the two dimensional computer in the Punizlan Institute, only one of the more advanced engineering creations in Arde.

During the last stretch of his journey, Yendred and his traveling companion, Tba Kryd, come under attack of a giant Bes Sallur, a snake like creature in Arde. The Bes Sallur, which can fly by trapping the air underneath it, traps the two travellers underneath its body and kills Tba Kryd. This situation truly shows how attached some in the class have become to Yendred, such as Alice. With the help of the class, who are very worried about Yendred's life at this point, Yendred is able to kill the Bes Sallur and escape with only an injured wrist.

Yendred finally finds Drebk, a character who seems to be able to enter a third dimension, even while on the two dimensional world of Arde. He is known for being able to disappear and then reappear in a different place, and it seems that the way in which he does this is by going into a third dimension and then coming back into two dimensions. Through his time with Yendred, Drebk takes him away from the computer science class. There is some knowledge that Derbk possesses and that Yendred desires to know. However, in learning it, he will have to give up his life as it is, including the communication with Dewdney's class, his friends.

The story in The Planiverse finally ends as Yendred leaves the two dimensional world with Drebk, leaving his Earth friends for good. This ends the novel with the speculation of perhaps the world having more than three dimensions. That perhaps a two dimensional world could exist, since no one could ever see it even if it was right in front of them since it would infinitesimally thin. Thus with great sadness, especially on Alice Little's part, the connection between Earth and Arde through the 2DWORLD simulation came to a halt.