Kohler's introduction to his major work on World War II, Guilt and Innocence in Hitler's Germany, the culmination of his years studying the aspects of the Nazi regime in the scope of its causes and effects, turns into The Tunnel, a brutally honest and subjective depiction of his own life and history and the opposite of the well-argued, researched and objective book he has just completed.

When the harsh reality of his work begins to dawn on him, he fears that his wife, Martha, will stumble onto his papers and read his most personal (and cruel) descriptions of his and their life.

During this time, he starts to dig a tunnel underneath the basement of his home, eventually hiding the dirt inside the drawers of his wife's collection of antique furniture.

The accompanying booklet prints Gass's overview of the novel's contents, structure, plot, "condition of the text", aim, cast, levels of organization, issues, and other matters.

In a 1995 radio interview at KCRW with Michael Silverblatt, Gass stated that the difficulty of the novel's early sections, which are introduced by a quote from Anaxagoras ("The descent to hell is the same from every place"), serve as both a false beginning to The Tunnel (the introduction Kohler is writing and his digging project) and as a test for the reader: "I think this is a standard modernist thing, but what it is is to make sure that the person who gets into the book is ready and deserves to be there.

Gass uses quite a bit of typographical variety in this section (a window and a Star of David, both constructed out of text, are notable examples) and includes pictures, drawings and watermarks.

The section ends with a long introduction of Kohler's mentor, Magus "Mad Meg" Tabor, which alternates from the professor's lectures to the narrator's memories of the man.

The character of Uncle Balt, a tall, sonorous farmer whose folksy pronouncements ("THEY'LL MAKE YOU INTO MAN JAM AND SERVE YOU ON TOAST") Kohler records and contemplates.

He describes his workspace, and meditates on his marriage, his book, and his colleagues, specifically Culp, an inveterate dirty limerick writer and the leader of Kohler's sons' boy scout troop.

Gass includes many of Culp's limericks (he's trying to write a history of the world using the form) and also brings back a few of the typographical inventions (a page designed to look like a paper sack; business cards) that dominated the novel's earlier sections.

The section mainly concerns itself with Kohler's recollections of his history professor, Tabor: his lectures, his conversational style, his philosophical influences and ideas, his illness and eventual demise.

Kohler invokes a youthful paramour, Susu, a gypsy lounge singer who committed atrocities against the Jews during World War II and was eventually executed by the Nazis.

Kohler recollects his father's attempts to teach him how to drive, as well as his bigoted reaction to foreigners (he dubs the head of the family "Mr. Toottoot") moving next door.

As I read, I found myself devastated by the thoroughness of the book's annihilating sensibility and revived by the beauty of its language, the complexity of its design, the melancholy, horror and stoic sympathy in its rendering of what we used to call the human condition.

"[5] In his review of the novel in the New York Times Christopher Lehmann-Haupt wrote: "So why, given the considerable grimness of The Tunnel, does the reader still track its endless coils of prose?