An experimental new test on the Enterprise's engines — courtesy of Starfleet engineer Kosinski (Stanley Kamel) and his mysterious alien assistant (Eric Menyuk) — sends the Enterprise careening beyond warp 10 and on an unintended (and quite impossible) journey millions of light years beyond the reaches of the Milky Way galaxy.
For the first time on Star Trek: TNG, we have a genuine sense of awe and wonder, where space no longer resembles a black star field but instead a colorful visage of the strange and unknown. The acceleration of the Enterprise beyond what was dreamed possible turns out to be the basis for a pretty good premise centering on the mystery of the assistant — known only as the Traveler — whose alien gifts have allowed the crew of the Enterprise to travel where quite literally no one has gone before. The question now is whether they can get back, especially with the Traveler having been weakened in getting here.
The episode is notable for at first seeming fresh and intriguing, but this feeling fades once it becomes clear that this place, wherever it is, has the ability to turn thoughts into reality. The episode has too many hallucination gags that become real threats, and all of it is based on pure fantasy rather than sci-fi. When anything can happen, and the best the writers can come up with are dead parents, Klingon pets, and flames blocking the corridor, it's kind of a fantasy-manufactured letdown. The Traveler has an intriguing dialog with Picard about the nature of exploration, but it goes on so long as to eventually become impenetrable.
The episode also provides a turning point for Wesley Crusher, whom the Traveler identifies as a science prodigy. Picard encourages this belief by making Wesley an acting ensign, but the problem with the character remains that he's too much of a cloying geek and you just want to strangle him.