Protector is a 1973 science fiction novel by American writer Larry Niven, set in his Known Space universe. It was nominated for the Hugo in 1974, and placed fourth in the annual Locus poll for that year. The work fleshes out a species called the Pak, originally introduced in a 1967 story called "The Adults", which forms the first half of the novel (there titled Phssthpok); the second half is titled Vandervecken. The Pak also appear in several of Niven's later works, including the later volumes of the Ringworld series and the novel Destroyer of Worlds which serves as a semi-sequel to Protector. Plot summary The novel comprises two phases in the same space that are separated by 220 years of time. Its central conceit is that Humans evolved from the juvenile stage of the Pak, a species with a distinct adult form ("Protectors") that has immense strength and intelligence and cares only about younger Pak of their bloodline. A key plot point is that transition to the Protector stage is mediated by consumption of the root of a particular plant called Tree-of-Life, which cannot be effectively cultivated on Earth. The first half of the book follows the path of a Pak named Phssthpok, who has travelled from the Pak homeworld in search of a colony of Pak in the distant system of Sol (our Solar System). Upon his arrival, he captures a Belter (a worker from the asteroid belt) named Jack Brennan, who is infected by Phssthpok's store of tree-of-life root and is transformed into a Protector (or at least a Human variant). They land on Mars where Brennan kills Phssthpok and is rescued by two Humans, Nick Sohl and Lucas Garner, who had set out to meet the alien. The first half of the novel ends with Brennan telling his story to the Humans before he heads for the outer reaches of the solar system. The second half of the book follows the path of a Human named Roy Truesdale who has been abducted with no memory of the event. While searching for his abductor, he befriends a Belter named Alice Jordan who helps him figure out that the man he has sought is none other than Jack Brennan. Truesdale and Jordan find Brennan in the outer solar system on a fabricated world of Brennan's design called Kobold. Brennan discovers that a Pak invasion fleet is headed towards