S4E19 · The Nth Degree

The teaser starts with Dr. Beverly Crusher and Lt. Reginald Barclay performing a scene from the 19th century play Cyrano de Bergerac. While Dr. Crusher performs well, Lt. Barclay struggles with his stuttering and anxiety, making mistakes and forgetting lines. As a minor character, this serves to re-introduce the viewer to Barclay and his typical extreme shyness and social awkwardness.

The Enterprise is sent to investigate the shutdown of the Argus Array, a deep-space telescope and radio antenna. Geordi La Forge and Lt. Barclay take a shuttlecraft to examine the array closely, discovering the presence of an alien probe nearby; the probe fires a pulse as they near it, disabling the shuttlecraft and knocking out Barclay. The Enterprise crew recovers the shuttle and are forced to destroy the probe when it follows the ship, believing the Argus Array was affected by a similar pulse. Barclay recovers, but the crew finds him much more intelligent than before. His IQ continues to increase, and La Forge finds that he has spent the night in a holodeck arguing quantum physics with Albert Einstein.

The Array starts to undergo a series of catastrophic failures. Barclay, with his newfound intelligence, casually explains how they can use the Enterprise computers to prevent the failures in only two days, much to his colleagues' disbelief. Barclay's solution works temporarily, but the failure rate increases, and Barclay finds the Enterprise computer too slow to keep up with it. He goes to the holodeck and creates a device that allows him to interact directly with the Enterprise and array computer systems, putting an end to the Array's failures. The crew finds that Barclay has become too integrated with the computer, and when they try to shut down the computer, Barclay sends the ship into a " subspace inversion", sending the ship across a great distance at a velocity significantly faster than conventional warp drive.

They arrive at the center of the Milky Way galaxy, and are met by a representative of a race of beings called the Cytherians, who are far more advanced than humans and find amusement in their " bipedal locomotion" and "hierarchical collective command structure". They free Barclay from the computer, and, minus his heightened intelligence, he arrives on the bridge to help explain what happened. The Cytherians are friendly explorers like the Federation, but instead of traveling to meet other races, they have launched probes that convey the necessary technical knowledge for other beings to come to them. The probe was unable to reprogram the Argus Array or the Enterprise shuttlecraft, causing them to fail. But it was able to reprogram Barclay, giving him the power to accomplish the task.

The Enterprise stays with the Cytherians for ten days, exchanging knowledge that will take decades to fully understand. The Cytherians then return the Enterprise to the Argus Array. Barclay finds himself back to normal, although he keeps vivid memories of his temporary transformation.