The Enterprise is sent to investigate the colonists of Omicron Ceti III. After three years of exposure to Berthold rays, the colonists are expected to be dead. The crew is surprised to find the colonists alive, happy and in perfect health. They have a perfect world. A world with no hate, violence, death or disease. They are vegetarians, who only farm what they need. It is a true paradise. Other members of the crew begin to become infected with the spores and some of the plants are beamed aboard the Enterprise where more of the crew are affected.