An exploratory spacecraft of the Galactic Corps, charged with opening up planets for human colonisation, sometimes by terraforming, crash-lands on an alien planet. They find that the ecology is heavy in ammonia, making the atmosphere unbreathable by humans, and the soil unsuitable for the Earth-type plants they have brought for colonisation.
As they are unable to take off again, the crew spend their time trying to adjust the environment to make it suitable for possible future human colonists, by cultivating Earth plants which will create oxygen. Although they spend many years at this task, they fail and, one by one, they die of ammonia poisoning.
As the last man dies, the flesh of the buried crew feeds the plants and finally helps them to flourish, providing the catalyst that alters the environment to become more Earth-like.