Geordi and Ro are invisible and intangible after a transporter accident.
The Enterprise helps a damaged Romulan ship, and during the rescue Geordi and Ro are caught in a transporter accident. Their crewmates believe them dead, but the pair have actually been shifted out of phase by an experimental Romulan cloaking device, so they can walk through walls while no one can see or hear them.
Wandering the ship, Ro thinks she has died, while Geordi insists there must be a scientific explanation. They uncover a Romulan scheme aimed at the Enterprise and find a way to be noticed using the ship's own systems. Restored to normal, they arrive in time for the lively memorial Data has organised for them.