A fleet of Martian spacecraft surrounds the world's major cities and all of humanity waits to see if the extraterrestrial visitors have, as they claim, "come in peace." U.S. President James Dale receives assurance from science professor Donald Kessler that the Martians' mission is a friendly one. But when a peaceful exchange ends in the total annihilation of the U.S. Congress, military men call for a full-scale nuclear retaliation.

Unable to move on from the loss of his daughter, Freddy, now a shell of the person he was before, swears to kill the man responsible for her death.

Seymour works in a skid row florist shop and is in love with his beautiful co-worker, Audrey. He creates a new plant that not only talks but cannot survive without human flesh and blood.