It introduces one of the most important but rarely seen races in the Known Space series: the Pak. The first half of the novel deals with a badly botched First Contact, and the second with the adventures of the titular Protector, the Super Strong, hyper-intelligent adult form of the Pak.
The first part of the novel is an expansion and partial re-write of the short story "The Adults" that was first published in 1967. The second part is a reworking of "Down in Flames", an un-used outline for a Beowulf Shaeffer story that would have served as a grand finale for Known Space and would have destroyed much of the setting. note
This novel provides examples of:
- Acrofatic: A minor Belter character is said to be so fat he couldn't support himself on Earth. He moves as easily as anyone else in zero-G.
- Adaptation Expansion: The first part of the novel is the same plot as "The Adults" with some small changes, but the ending is different and considerably more complicated. It also changes the names of two of the belters who crew the Blue Ox, including making one of them a woman.
- Artificial Gravity: The first Pak ship has a gravity polarizer, which cannot really create gravity but can somewhat "redirect" existing gravitational fields, acting as a hang glider. Brennan, the human Protector reverse-engineers it and creates Artificial Gravity proper.
- Bizarre Alien Biology: The Pak. They spend their childhood and adult lives as barely-intelligent tree-dwellers, and then, upon reaching old age, begin craving the Tree-of-Life, which transforms them into an extremely intelligent, extremely strong Protector form. The Protector has no free will, because it must constantly protect its descendants at the cost of everyone else, or else it involuntarily starves itself. Only, it's not Bizarre Alien Biology, since they're Homo Habilis or their direct ancestors. Also the Tree-of-Life, which is like a sweet potato, only it has a symbiotic virus living in it. The virus alters the Pak DNA to cause the Protector stage, and it works for humans, more or less.
- Blue-and-Orange Morality: The Pak Protectors have one moral code, and one moral code alone; protect their family at any cost. If they need to nuke a planet to save one of their bloodline, they will. If their bloodline is gone, they loose all desire to eat and peacefully let themselves die. It's for this reason that the Forever War on their homeworld hasn't killed them yet, because they all realize that extinction of the symbiotic root that gives them their intelligence will doom their entire species, and thus their bloodlines.
- Do Unto Others Before They Do Unto Us: A staple of Pak Protector psychology (see Obstructive Code of Conduct below), which is why their planet is a constant battleground (see Forever War). It's not out of cynicism, either: Pak Protectors have very limited free will, despite — or better, because of — their great intelligence.
- Downer Ending: After working tirelessly in solitude for the betterment of Mankind for nearly two hundred years, Brennan realizes that the only way to save humanity from the Pak colony fleet is to infect the colony world Home with a strain of the Pak virus that will kill everyone too old or too young to become a protector, and cause the change in everyone else, so that he will have an army of childless Protectors to fight the Pak. Horrified at this plan - which Brennan has kept secret from him, Truesdale kills Brennan, who can't fight back effectively against a breeder-stage human who is one of his descendants. In fact, Brennan's last act before dying of his injuries is to administer the first aid that saves Truesdale's life. Shortly afterwards, Truesdale, who was already infected with the virus, transitions to Protector, and immediately understands that Brennan's plan was the only feasible one - meaning that Brennan died for nothing. The Home colony becomes extinct, and the new army of childless protectors heads off to war, but the last page reveals that the reader will have this story in his hands only if Truesdale's army has been defeated, and Truesdale himself is dead. Later stories don't mention a Pak invasion fleet destroying Earth and say that Home was eventually re-colonized, but the fate of Truesdale and his army is left unresolved.
- Fantastic Racism: There's a tinge of it in the relationship between Belters, humans who live and mine in space, and Flatlanders, who live on Earth. Belters are tall, unmuscular, and tan almost black in the unfiltered light of the sun, and they're quick to disparage Flatlanders and Earth in general. Emigrating to the belt has its own stigma from both sides, too.
- Forever War: What the Pak Homeworld is like, although given Pak social organization it can also be seen as Feuding Families writ large. Each Protector fights to protect its own bloodline and kill different bloodlines that may pose a problem in the future, all while making and dissolving unstable alliances. Factor in that Protectors are smart enough to invent a new Weapon of Mass Destruction each month, and it's clear to see see why few places on the planet are not constantly devastated by war.
- Great Big Library of Everything: There's one on the Pak Homeworld. Unlike many other instances of this trope, it's very badly organized, since the Pak don't value knowledge for knowledge's sake.
- Guilt-Free Extermination War: The human Protector kills all the Martians with a Colony Drop, to protect his "descendants," humanity, without any remorse. In fact, he's somewhat proud of it.
- Human Aliens: So human, they evolved into us.
- Humans Are Smelly: The Pak Protectors maintain their racial purity by smell. Homo Sapiens look wrong to them, but a much bigger deal to them is that we also smell wrong.
- Humans Are Superior: Humans could potentially beat the Pak, according to some characters, because we can cooperate to develop technology, whereas they can only build things that will protect their descendants. The Pak also fight amongst themselves too much to ever build a lasting civilization.
- My Brain Is Big: Becoming a Protector involves, among other things, the brain growing much larger and evolving a more complex structurenote . Human who become Protectors are this to Pak Protectors, since their brains are larger to start with.
- Obstructive Code of Conduct: The Pak Protectors are so adept at logic that they can instantly see the best way to protect their descendants, and they're unable to choose to do anything else. The human protector claims it doesn't apply to him, but he's not convincing anyone.
- Oh, Crap!: The plot of Protector runs on these.
- The Pak colonist protectors have a Mass "Oh, Crap!" when tree-of-life doesn't grow right in the colony.
- Phssthpok has an Oh, Crap! when his native Valley of Pitchok is nuked and his life expectancy is now tied to that of his youngest surviving granddaughter.
- The Pak protectors have a Mass "Oh, Crap!" when they realize local space is becoming inhospitable.
- Phssthpok has another one when he catches engine problems—and just barely has enough time to stop the ship exploding.
- Nick Sohl and Einar Nillson have one when they realize a local smuggler has taken it into his head to contact the Outsider himself.
- Jack Brennan and Einar Nillson have Oh, Crap! moments when they realize they have this overwhelming urge to eat this unknown alien root.
- Tina Jordan has an Oh, Crap! moment when Nillson suddenly takes a bite out of the alien root they are analyzing, and then attacks her when she tries to stop him from eating more.
- Brennan has one when he realizes what Phssthpok will do if he realizes humanity lacks the Pak's Chronic Backstabbing Disorder.
- Brennan has one years later when he realizes the Pak have evacuated their homeworld and are coming to Earth.
- Truesdale has one when he realizes just what Brennan's plan for the people of Home is.
- The people of Home have a Mass "Oh, Crap!" when they realize that whatever this new virus is, it's spreading itself intelligently.
- Omniscient Morality License: Human Protectors are capable of thinking of humanity as an abstract whole and sacrificing entire planets to ensure the survival of the species. Though they need to be separated from their direct descendants first.
- Ram Scoop: The novel's method of interstellar travel.
- Schizo Tech: Due to the Pak's uneven interest in technology, their ship is far ahead of human development in some respects — most notably, the gravity polarizer resists reverse-engineering attempts for two centuries — but behind it in others, such a very inefficient fusion reactor and no autopilot. It doesn't help that the ship is pretty much a prototype. The second Pak fleet has much improved tech.
- Super-Intelligence: Pak Protectors are smarter than humans can ever hope to be unless they become Protectors themselves. Human protectors are likely to be even smarter, since their original form is smarter to begin with.
- Synthetic Plague:
- Common weapons in the chronic wars between Pak Protectors as they don't damage farmland.
- Brennan creates an aerosolized version of the Tree of Life virus that kills everyone too young or too old to transform to the protector stage on Home.
- The Unfettered: Protectors do not care about anything except the protection of their bloodlines. Nothing else matters. Pak Protectors who outlive their descendants tend to become suicidally depressed and are only capable of motivating themselves to stay alive by dedicating themselves to a greater cause, Phssthpok had his bloodline sterilized by radioactive fallout and hoped to be able to "adopt" a lost Pak colony.
- Trans Human Treachery: Any Human that becomes a Protector acquires the inability to harm members of their own bloodlines, but like the Pak they seem to have little consideration for the welfare of humans who are not their descendants.
- Truesdale kills Brennen trying to prevent him from infecting the inhabitants of Home with Tree-of-life virus, but once he transitions to protector himself he immediately decides Brennen was right and starts spreading the virus.
- Some of the new protectors on Home try to save their families by protecting them from the Tree-of-life virus. Truesdale says it's only necessary for his group to confine the protectors while ensuring their families are exposed. Once all of the family members are dead or transitioning to protector they let the now childless protectors free and they willingly join Truesdale's group.
