A mysterious probe turns Barclay into a genius.
A strange probe affects Lieutenant Barclay, and he starts to become far more intelligent. At first he is delighted, as his talents lead him to surprising new accomplishments, and his colleagues treat him with new respect. But his growing powers begin to change him in ways that are alarming.
The Enterprise is drawn toward the center of the galaxy and encounters the Cytherians, a group of beings who are behind the probe. The story is a thoughtful take on the idea of intelligence and what it means to understand. It also allowed Barclay to return as a more confident figure, and Barclay's moment of triumph is one of the high points of the fourth season.