Matt Helm is to captain the last space shuttle carrying passengers to the starship, but his irrepressible desire for Fern Angelus corrupts his sense of duty. He agrees to take part in her time experiments.
Set against a background of passion and longing, Matt's uncanny success with mind projection meets unforseen complications. He projects his mind to a future Earth: a world of shallow, extensive seas, mutated trees growing in layers on each other's branches, and strangely evolved animals like snappersnouts, humpers and energy creatures.
Matt's strange visions eventually meet reality when he discovers that the last load of passengers for the starship has been left behind; and he is one of them.
The 'Joy Juice' is the vital life fluid extracted from the workers, the second class citizens whose life is a constant search for and movement from one trip, one hallucination to the next. It is only when the workers are tripping that the Uppers can extract the 'Joy Juice'.
But what happens when the good trips turn into bad ones? When pleasant dreams become nightmares?