She calls him Teacher, and together they encounter several other strange beings as they travel through the ship trying to survive and find the answers to their questions.

One faction wants to abandon their mission to colonize a planet which is already teeming with life, while the other wants to press forward.

Teacher, who discovers his real name is Sanjay, eventually reaches the third hull of the book's title where he encounters Mother, who is the leader of the faction that wants to continue to their destination.

[2] Chris Hsiang summarizes the overall impact of the book as "...less than thrilling but I've come to expect this from Greg Bear: he is often more concerned with the journey than the destination.

"[3] Similarly, the book has been described by Harriet Klausner of Alternative Worlds as a "science fiction thriller that adds very little new to the generational ark in space subgenre".