The Cat Who Walks Through Walls is a science fiction novel by American writer Robert A. Heinlein, published in 1985. Like many of his later novels, it features Lazarus Long and Jubal Harshaw as supporting characters.
Plot summary
A writer seated at the best restaurant of the space habitat "Golden Rule" is approached by a man who urges him that "Tolliver must die" and is himself shot before the writer's eyes. The writer—Colonel Colin Campbell, living under a number of aliases including his pen name "Richard Ames"—is joined by a beautiful and sophisticated lady, Gwendolyn Novak, who helps him flee to Luna with a bonsai maple and a would-be murderer ("Bill"). After escaping to the Moon, Gwen claims to have been present during the revolt described in The Moon Is a Harsh Mistress.
Still pursued by assassins, Campbell and Novak are rescued by an organization known as the Time Corps under the leadership of Lazarus Long. After giving Campbell a new foot to replace one lost in combat years before, the Time Corps attempts to recruit Campbell for a special mission. Accepting only on Gwen's account, Campbell agrees to assist a team to retrieve the decommissioned Mike, a sentient computer introduced in The Moon Is a Harsh Mistress. Engaged in frequent time-travel, the Time Corps has been responsible for changing various events in the past, creating an alternate universe with every time-line they disrupt. Mike's assistance is needed in order to accurately predict the conditions and following events in each of the new universes created. Campbell's frequent would-be assassins are revealed to be members of contemporary agencies also engaged in time manipulation who, for unknown reasons, do not want to see Mike rescued by the Time Corps.
During the mission, Gwen is grievously wounded and Campbell loses his foot again, though the Time Corps succeed in retrieving Mike. The story ends with Campbell talking into a recorder (presumably the source of the first-person narrative) reflecting on the mission and his relationship with Gwen.
Background
The Cat Who Walks Through Walls may be regarded as part of Heinlein's multiverse series, or as a sequel to both The Number of the Beast a Heinlein character originally introduced in Methuselah's Children and who reappeared in Time Enough for Love, The Number of the Beast, and To Sail Beyond the Sunset. Also appearing are Jubal Harshaw, a major character in Stranger in a Strange Land; Galahad, of Time Enough for Love; and Manuel Garcia O'Kelly Davis, the first-person protagonist of The Moon Is a Harsh Mistress.
Reception
Dave Langford reviewed The Cat Who Walks Through Walls for White Dwarf #76, and stated that "I'm afraid it's Heinlein self-indulgence time again. What's on the menu is those blasted inter-universal travellers from Number of the Beast, plus walk-ons from Time Enough for Love, Glory Road, The Moon is a Harsh Mistress, Stranger in a Strange Land and more."
Wendy Graham reviewed The Cat Who Walks Through Walls for Adventurer magazine and stated that "About the only thing I liked about the second half was the cat, Pixel, of the title. I would suspect that Robert Heinlein, Patrick Moore and I have one thing in common — we have all been adopted by a cat (they do that you know!) And I like my books to have endings."