Dorothy "Dory" Valentine is a wildlife biology PhD candidate studying meerkats at the Kalahari Research Centre in southern Africa when a lion attacks and kills her. A beam of light pulls both her and the lion into an alien spacecraft, where she awakens floating in a green-liquid tank surrounded by pods containing unconscious human women. Fighting off the ship's crew of small owl-like aliens called Biwban, Dory accidentally absorbs a blue substance, frees the lion, and escapes in a pod. The lion leaps in at the last second.
The pod crash-lands in a lake on an unknown planet, where a mosasaur, a marine reptile millions of years extinct, destroys the vessel. A gray-skinned alien on the beach saves them by shooting fireballs at the creature. When the lion speaks, Dory realizes the blue substance functions as a translator symbiont activated through mouth-to-mouth contact. She names the lion Toto, after the dog in
The Wizard of Oz. Toto explains he attacked Dory because aluminum lodged in his gum drove him toward soft prey; Dory removes it, and the two form an uneasy alliance.
The alien leads them through jungle teeming with species from wildly different geologic periods: stegosaurs, pterodactyls, and ice-age ground sloths. After Dory removes her wet boots by a fire, the alien recoils in horror at her bare toes, mistaking them for a disease called hoof rot. When Dory kisses the alien for sharing food, the translator activates between them. He introduces himself as Sol, a monster hunter of the Night Ridge clan. Sol is a Sankado, a horned, hooved, fire-breathing species whose surviving members were deposited on this planet roughly 10 years earlier by the Biwban after a toxic spill from a crashed cargo ship destroyed their home world, Sankatul.
The next day, Dory gets caught in a snare trap and is discovered by a second Sankado, a large purple-skinned male with ram-like horns. Sol attacks, assuming the stranger is hostile, but Dory kisses the newcomer to transfer the translator. The stranger introduces himself as Lokbaatar, or Lok. A cloaked Biwban drone fires darts that hit both Lok and Sol. Toto knocks the drone from the sky, revealing a tiny Biwban behavioral observation intern inside.
After Dory transfers the translator to the panicked intern, he realizes the Sankado and humans are sentient "class A species," the Biwban's highest category of protected beings, meaning the Biwban have violated galactic law. A company called Fuel X poisoned Sankatul's ocean with a crashed cargo ship, and the Biwban government forced the company to fund a Biodiversity Conservation Initiative (BCI) to relocate survivors to a terraformed world. The field team rescued only male Sankado, having mistaken physical sex differences for color variation, and abducted human women as genetically compatible mates, taking only women already near death. The planet's dinosaurs were cloned from DNA collected at Earth museums.
The darts contain a Nexus serum that triggers a permanent mating bond called Zhali among the Sankado. Dory is now bonded to both Sol and Lok for life. She grieves the loss of her PhD, her career, and her old life, but Toto urges her to embrace the adventure ahead. When Dory discovers the Biwban failed to remove her Nexplanon birth control implant, she formulates a plan: follow the mate bond, force the intern to guide them to the BCI research center, and punch the department head.
The group travels toward the research center on Lok's parasaurolophus mounts and reaches a cul-de-sac of Biwban-built "enrichment" houses, where the intern tracks Dory's affection levels toward each mate and sabotages every attempt she makes to sleep apart from them. Sol warns Dory that Lok is actually General Ghoszi Lokbaatar of the Singing Arrows, his former military clan, and a legendary war general. Lok, overhearing, confirms this but explains that after the Calamity destroyed their world, he abandoned his title, left his armor at a monument called the Glyph Stone, and chose peace.
When the Gruulorak, a massive one-armed pink T. rex, attacks the settlement, the group is scattered. Dory sprays dog shampoo in the creature's nostrils to save the pinned Sol, but a monsoon separates them: Dory escapes with Lok while Sol, Toto, and the intern flee in another direction.
Dory sneaks out at dawn to find Sol and is captured by King Osid's forces. Osid rules the united Dulba Empire from a fortress that stampeding dinosaurs destroy each year during a migration called the Rumbling. Inside, Dory finds Toto caged alongside Blair, a punk rocker with purple hair who also escaped the Biwban ship; the intern, under Osid's coercion, bonds Blair to the king with the Nexus serum. Osid needs Lok's warriors; he poisons Dory with a barbed wispfruit, sends her bloodied bandage to lure Lok to a duel, and coats Lok's armor with a second toxin. Blair breaks free using a hidden revolver and shoots Osid, grazing his face, but his warriors force compliance.
When an explosion knocks Dory into the fortress lake, she has a dreamlike vision and realizes the fortress is built in the dinosaur migration path; relocating would solve the problem. Sol escapes during a breakout staged by Lok's warriors and rescues Dory. She brandishes her bare foot, screaming about hoof rot, and the soldiers flee. The group shelters in a Biwban-built chapel decorated with vintage cartoon characters, most prominently Steamboat Willie. The intern reveals he has been engineering the group's separations because "pining" raises Dory's affection meters, and he signals Biwban hovercrafts to recapture her. Sol destroys several ships with his fire and confesses his love for Dory.
The group reaches the Glyph Stone, where Lok's warriors are strapping him into his poisoned armor for the duel. Dory screams for him to stop, and Sol helps cut the straps, but Lok's throat is already closing. Recognizing anaphylactic shock, Dory inserts a hollow reed into his nostril as a makeshift airway tube, saving his life. She tells both men she loves them and reveals her birth control implant; both express relief, agreeing they are not ready for children.
King Osid arrives with his war party and demands Lok fight. During the duel, Blair breaks free and fires at Osid, but the bullet grazes Dory's temple. Bloodied but standing, Dory forces both rulers to stop and presents her analysis: Relocating the fortress out of the migration path will solve Osid's problem. She advises him to find the compound where the abducted women are held and rebuild near it. Osid accepts, and Dory collapses from the wispfruit poison. The intern arrives with Biwban hovercrafts, captures Blair and Osid for mandatory couples counseling, and transports Dory's group to the research center.
At the BCI center, Dory is cured. When the doctor questions why she has not conceived, Sol claims humans require chocolate and coffee to reproduce, building on a lie Dory earlier told the intern. Dory marches into the office of Vexil Krynn, the BCI department head whose father's negligence destroyed Sankatul, and punches him unconscious. She cannot return to Earth, but she has found love, purpose, and a planet full of impossible animals to study. The group sets out to free the other abducted women. In an epilogue, the intern is promoted to Field Agent 527, code-named Cupid, tasked with overseeing the remaining human-Sankado pairings.