As a child, his planet was invaded, and all were killed, except for Barash and his mother, who hid him on Alpha Onias III, where she hoped their species' enemies would never find him. She installed neural scanners and holographic projectors in a cave for Barash to live. They could read his mind and fulfill his desires and needs. However, the fantasies the scanners created were no substitute for real interaction with other sentient beings, and he became very lonely.
In early 2367, the USS Enterprise-D was in the area and detected the energy probes from Alpha Onias III. Commander William T. Riker led an away team to the cavern. Barash decided to trap Riker in a complex holographic fantasy in the hope that he would keep him company. The members of the away team were overcome by volcanic gases. Lieutenant Worf and Lieutenant Commander Geordi La Forge were beamed back to the Enterprise-D, but Riker was trapped on the planet.
Using the neural scanners, Barash created a version of the Enterprise-D now sixteen years into the future into which Riker awoke. Dr. Crusher claimed that he had been infected by Altarian encephalitis and had lost all memories since Alpha Onias III. He was now captain of the Enterprise-D and a single parent with one slightly troublesome child, "Jean-Luc Riker", the role that Barash assumed. "Admiral" Picard then arrived on a Romulan warbird with a diplomatic delegation. Riker was to complete the final peace accords with the Romulans, which he had been working on ever since the Enterprise-D rescued a damaged Romulan ship. Although Riker began to accept his new circumstances and give the young "Jean-Luc" attention, the simulation quickly began to fall apart as the neural scanner technology was not able to keep up with Riker. In the simulation, the Enterprise-D computer was much too slow and the senior staff were unable to answer Riker's questions about the previous sixteen years. Moreover, a recording of his wife revealed Minuet, a former holographic fantasy of Riker's.
Barash attempted a different reality when Riker confronted the characters. This illusion then gave way to another, in which Riker was imprisoned in a Romulan laboratory. Barash stayed in the form of the child, but now called "Ethan". Riker and "Ethan" plotted an escape, but Riker figured out this second deception when "Ethan" accidentally called Tomalak "ambassador", a rank he held only in the first illusion. Barash then revealed his true nature to Riker. Will offered him safety and companionship aboard the Enterprise-D, and the two were transported back to the ship. (TNG: "Future Imperfect")
Barash was played by background actress Dana Tjulander, who received no credit for her appearance.
According to an internal reference document, listing all the aliens seen in Star Trek: The Next Generation, which was circulated around the time of the production of TNG Season 5, Barash was given the description of "a short, willowy alien of undetermined gender."
Barash's true form bore a strong resemblance to the "Grey aliens" of UFO folklore.