[1] Passage follows the efforts of Joanna Lander, a research psychologist, to understand the phenomenon of near-death experiences (or NDEs) by interviewing hospital patients after they are revived following clinical death.

Her work with Dr. Richard Wright, a neurologist who has discovered a way to chemically induce an artificial NDE and conduct an "RIPT" brain scan during the experience, leads her to the discovery of the biological purpose of NDEs.

[3] In a review of the book, science fiction scholar Gary K. Wolfe writes, "Willis tries something truly astonishing: without resorting to supernaturalism on the one hand or clinical reportage on the other, without forgoing her central metaphor, she seeks to lift the veil on what actually happens inside a dying mind.

[6] Joanna Lander, a clinical psychologist, interviews patients who have had near-death experiences; she aspires to understand what occurs between the times when a person dies and then is revived.

She realizes that the scientific evidence is contaminated by the influence of Dr. Maurice Mandrake, a persistent and almost omnipresent charlatan "researcher" who publishes best-selling books about near-death experiences and convinces patients that their experiences happened exactly the way his books describe NDEs, such as learning cosmic secrets from angels: They remembered it all for him, leaving their body and entering the tunnel and meeting Jesus, remembered the Light and the Life Review and the Meetings with Deceased Loved Ones.

Mandrake's method is to ask mellifluous leading questions of the patients and thereby taint their self-reported NDEs; this causes Joanna and Richard hardship in finding un-interviewed volunteers for their own study.

Before she can tell Richard Wright about her discovery, she goes to visit Nurse Vielle in the Emergency Room and is stabbed by a man deranged by a drug called "rogue".

Richard Wright, on hearing that Joanna is dying or dead, enters an artificial NDE, thinking that he will find himself in the Titanic and be able to rescue Lander.

He instead finds himself at the offices of the White Star Line, where the names of the victims of the Titanic disaster are being read to the public - he is too late to "save" Joanna.

Within her final NDE, on an imaginary ship, Joanna finds herself adrift on the water, with some memories still intact and accompanied by a child and a dog which Maisie has told her about from other disasters.

When they gather to watch movies one night, Vielle tells Richard, "As if talking to patients about their NDEs isn't bad enough, in her spare time Joanna researches famous people's last words.

They include Coma, Fight Club, Final Destination, Flatliners, Harold and Maude, and Peter Pan, as well as The Twilight Zone and The X-Files.

"[12]Gary K. Wolfe, the first of many Locus reviewers to discuss the book at time of publication, compares the novel at many points with Willis's Lincoln's Dreams and writes: Apart from its simple virtues as a compelling story on an irresistible theme, Connie Willis's big, ambitious new novel Passage should be of particular interest to her readers because of the ways in which it recapitulates major preoccupations and techniques of her career to date, and because in it she seems fiercely determined to show us everything she's got... Each makes historical research a major vector of narrative suspense, with specific historical details—the Civil War in Lincoln's Dreams, the sinking of the Titanic here—treated as though they were clues in a murder mystery.

[13] Wolfe continues: Like Doomsday Book (1992), it grapples with one of the grandest of all themes, death, and uses the inability of major characters to communicate key bits of information to each other as another suspense device.

The book's multiplying internal and external mazes provide an emblem of human complexity, foolishness, and deeper terrors, some reaching from beyond death.

Willis' trademark habit of making some set of frustrating everyday-life details a recurring motif or running joke (in this case, the difficulty of navigating the hospital corridors, plus the never-open cafeteria) is over-extended here...";[17] conversely, reviewer Steven Wu felt that "Part One of the book is masterful, with several chilling scenes, a compelling mystery, and a doozy of a cliffhanger ending.