Lock In, the new science fiction novel by Hugo winner John Scalzi, boasts the density of a red dwarf. It’s a hardboiled detective novel, and a surprisingly plausible “future history,” and an exploration of identity and states of consciousness, all in one relatively short volume. The real mystery is how Scalzi crammed so much fascinating material between two covers.

The premise of Lock In, and the imagined reality to which the title refers, is the shocking result of a mutated flu virus. As the fictional “editor” of Unlocked: An Oral History of Haden’s Syndrome explains:

Twenty-five years ago [about 2020], doctors and hospitals were receiving their first cases of the disease that was initially misdiagnosed as a variant of the Influenza A virus subtype H5N1, and then briefly known as “The Super Bowl Flu,” and “The Great Flu,” and then finally, after the full extent of the damage it could cause was known, named “Haden’s syndrome.” The disease would claim millions of lives and sentence millions more to “Lock In,” a paralysis of the body that leaves the mind fully functional.

(Unlocked, a short mockumentary e-text after the pattern of Max Brooks’s original World War Z, was distributed (though not very widely) for free as a marketing hook for Lock In. Unlocked is still for sale at Amazon.com for 99 cents, and reading it before Lock In will make the latter much less challenging to read.)

Haden’s Syndrome is named after the First Lady, Margie Haden, the first celebrity sufferer of the disease. She and millions of Hadens, as they come to be called, suffer multiple rounds of symptoms. The first looks like a bad case of an ordinary flu. It recedes, then returns with all the symptoms of meningitis. That second round kills most people. Those who survive are “locked in” as described above—fully aware and mentally capable, but completely physically paralyzed. A very small minority of those survivors, a number in the five figures, retain their bodies’ functionality but see their brains restructured much like the locked in. These people can act as Integrators: hosts for the consciousness/will of others—bodies available for loan, as it were.

Because Haden’s Syndrome hits the President of the U.S.A.’s beloved wife in its first wave, then spreads so widely and rapidly, Washington pours unprecedented resources into researching and treating the disease. At the time Scalzi’s story begins, a backlash to this funding is just gaining strength, in the form of a cost-slashing measure called the Abrams-Kettering Bill.

That brings three key Haden’s-related technologies front and center for Scalzi’s murder mystery plot. First there are “threeps.” As Unlocked explains, engineers develop neural networks for implantation into Hadens’ brains; the networks allow them to live and move about in the world via realistic robotic body simulators. Their brains—physically stuck in bed, but effectively out in the world—hear, feel, smell, and see what their robot bodies experience. When Margie Haden tries the first model and looks in the mirror at “herself,” the metal body in which her projected consciousness is walking around, she exclaims “I look just like C3PO!” The robots are thus nicknamed “threeps,” and the tag sticks. Scalzi’s narrator, brand-new FBI Agent Chris Shane, occupies—and demolishes or severely damages—several threeps while tracking down the murderer. Laws treat a threep almost exactly like a “real” human; to attack and destroy a threep is to incur murder charges. A schism develops, and is coming to head, during the course of the investigation. One faction of Hadens, accustomed to interacting “normally” with the outside world, opposes a separatist faction that turns inward toward other Hadens. Unlocked compares the schism to a similar one existing among the deaf in our time.

The separatist faction widely, and constantly, employs the second key Haden’s-related technology: the Agora. Named after the ancient Greek venue for debate and discussion, the Agora is a kind of mental gathering place fully available only to Hadens. (The separatists, and Agent Shane too, reject the labels “victims” and “sufferers.” They prefer simply “Hadens,” the neutral descriptive term.) Hadens gain access to the Agora via their implanted neural networks. It functions like a chatroom, a message board, and an email system, but one in which as far as participants’ brains are concerned, they’re physically present. Each Haden there creates her/his own fairly literal mental space, which can look like anything: a dark cave, Skeletor’s castle, a mountain meadow, or whatever. The Agora’s future, its accessibility, turns out to be vitally connected to the murders and the investigation.

Skeletor’s Castle—a Haden’s personal space on the Agora?

The final key relevant technology is the functioning of Integrators. Typically, and on purpose, Integrators maintain veto power: if the consciousness borrowing their body starts to do something super-stupid and/or suicidal, the host, present though muted, can nix the proposed action and report its instigator. Two important facts of the detective story have to do with Integrators. Agent Vann, Shane’s veteran partner, is a former Integrator; she was one briefly, years ago, but she quit that line of work. Why? That’s a gripping story-within-the-story closely related to the mystery’s solution. Also, two Integrators commit suicide in quick succession, an unheard-of and supposedly impossible eventuality. Why? Again, see the mystery’s solution.

Put all this together and look at how much Scalzi has jammed into 337 pages. There’s a fully developed hardboiled detective novel, which is plenty for that space by itself. Then there is also the amazingly rich “future history” of Haden’s Syndrome. Max Brooks took about the same number of pages to (productively and entertainingly) spin out World War Z, regarding an arguably much simpler premise—a virus kills people and turns them into zombies.

World War Z, a rough analog with Lock In’s companion volume, Unlocked.

Lock In contains the potential for several science fiction “novels of ideas” based on Haden’s Syndrome lore: explorations of the Agora’s possibilities and uses; of the dual consciousness of “meatspace” body and threep, and their complex relationship; and of the possible uses and abuses of Integrators. Then, too, the relationship between Hadens and non-Hadens makes a fascinating study in itself. Unlocked devotes a few pages to non-Hadens’ interactions with the earliest threep models. For example:

[With t]he first Margaret Haden prototype Charlie [the engineer who developed the first threep] took things too literally and tried to make it look like Margaret Haden, including a representation of her face. It was creepy. There’s a concept called “the uncanny valley,” in which something that’s almost but not quite human is repulsive because you’re so very aware of it being fake. This was that.

The concept could easily be spun out to a few hundred intriguing pages. So, too, could the complexities that would have to be involved in effectively renting a person’s body for a day or two—the ordinary function of Integrators.

In this way, Lock In is a bit frustrating to read. The detective novel form dominates the story, relegating the story of Haden’s Syndrome to squeezed-in, throwaway expository lines. I kept wishing the detective story would back off for a while so I could hear more about Haden’s. I don’t know of any plans John Scalzi has to do so, but I sincerely hope he will revisit the incredibly rich world-building that is currently underutilized as a mere backdrop to Lock In, and turn it into a whole series of novels about the Agora, Hadens’ consciousness, threeps, and Integrators.