Episode 4 (S01E04)

Arthur discovers the Great Project, which involves Deep Thought, the second most powerful computer ever made, designed to reveal the Ultimate Question of Life, the Universe, and Everything. After a lengthy wait, the computer finally returns with its answer: 42. The scientists are understandably frustrated, especially since Deep Thought can't specify what the Ultimate Question actually is. This leads to the necessity of constructing a new computer, named Earth, to uncover it. Meanwhile, Trillian's pet mice, who now own the Great Project, plan to dissect Arthur’s brain to find the Question. Just when things seem dire, the crew becomes trapped behind a wall of malfunctioning computers.