The Enterprise-D docks at Starbase 133, where Dr. Crusher greets her elderly friend and mentor, Dr. Dalen Quaice. After taking him to his quarters discussing the loss of old friends, Dr. Crusher visits her son Wesley Crusher in Engineering. Wesley attempts to create a static warp bubble but the experiment appears to fail. As the Enterprise leaves Starbase, Dr. Crusher finds that Dr. Quaice seems to have gone missing, with no record of him coming aboard the ship. As she performs a medical test on transporter chief O'Brien, she realizes she is the only one in Sick Bay; further investigation and discussion with the crew shows that she has always worked alone in Sick Bay.
Dr. Crusher continues to try to track down the disappearing people, and finds more and more crew members that she remembers being completely unknown to the crew or the computer. At one point, a vortex appears near Dr. Crusher and attempts to pull her in, but she is able to hold on to a fixture until it dissipates; the ship shows no record of the vortex's appearance when she investigates. Eventually, no one but Captain Picard and herself remain on the ship, but Picard believes that the situation is normal. Dr. Crusher orders the computer to give Picard's vital signs over the ship's speakers so that she knows he is still there, but shortly thereafter even he disappears. Then the vortex reappears, and once again tries to claim Beverly. She is blown across the bridge, but she manages to hang onto Data's chair until the vortex disappears.
At this point, the viewer is shown the actual Enterprise, where Wesley had successfully created the warp bubble, trapping his mother within it. With the warp bubble collapsing rapidly, Wesley's fears lead The Traveler to appear and help Wesley attempt to stabilize the bubble. The Traveler recommends the Enterprise returns to the Starbase, where the warp bubble was formed and may be more stable.
Within the warp bubble, Dr. Crusher attempts to direct the Enterprise to the home planet of the Traveler, but soon finds the ship is unable to set that destination as it no longer exists. More of the universe she knows disappears, soon leaving only the Enterprise. She recognizes the shape as being that of Wesley's warp bubbles, and determines that she is trapped, the earlier vortex being the Enterprise crew's first attempt to save her. As the warp bubble shrinks, erasing parts of the Enterprise, she races for Engineering, the center of the warp bubble, and finds a vortex waiting there. She jumps in at the last moment, finding herself back in Engineering along with Picard, Wesley, and the Traveler. After assuring that everyone she knows, including her guest Dr. Quaice, is aboard the Enterprise, she thanks the Traveler for his help.