After her first trip by transporter, Sato seems to fade from existence, unseen and unheard by her crewmates, who believe she has died.
Sato reluctantly uses the transporter for the first time to escape a storm. Back on the ship, she begins to feel that something is wrong, and soon she becomes invisible and inaudible to her crewmates, who believe she has died.
In her ghostly state, she discovers aliens planting a bomb aboard Enterprise and tries to warn the crew. In the end the whole experience takes place within the seconds she is in the transporter beam, as the crew works to rematerialize her. The episode was directed by David Straiton and written by Rick Berman and Brannon Braga.