Elliot Kintner and his daughter Ridley accidentally run over a unicorn foal while driving to their boss Odell Leopold's estate. After discovering the unicorn's magical healing abilities, the Kintners hide it in their car. Ridley experiences cosmic visions from touching its horn, and the unicorn's blood cures Elliot's vision and allergies. The Leopolds' assistant, Shaw, shoots the unicorn after learning about its powers. Scientists at the Leopolds' estate, led by Dr. Song, extract the unicorn’s horn to cure Odell's cancer, but tensions rise when Ridley warns against exploiting it.

Odell orders more testing, but the unicorn's parents, two larger unicorns, attack and kill several people, including Dr. Song. Meanwhile, Shepard, Odell's son, steals the unicorn's horn and orders a scientist to remove the rest. Ridley tries to warn Elliot, but the hunting party is ambushed by the adult unicorns. The survivors plan to appease the unicorns by offering them their foal, but the unicorns kill more people after discovering the horn is missing.

The final confrontation leads to tragic deaths, including Elliot's, but the unicorns use their magic to revive him. The Kintners are arrested, and as they are driven to jail, the unicorns save them by ramming the police car, causing it to crash.