While the crew sleeps in comas to cross a dangerous region, Phlox runs the ship alone and begins to doubt what he is seeing.
Enterprise must pass through a region of space whose radiation would harm humans, so Phlox places the crew in comas for four days. T'Pol appears to remain awake with him, and the two run the ship.
As time passes, the disturbance affects Phlox's mind and he begins to see strange things, including a zombie-like Sato. When the region grows larger than expected, he must master the warp drive to get the ship out. Escorting T'Pol to her quarters, he finds the real T'Pol asleep there, sedated with the rest of the crew, and his companion vanishes. The episode was directed by Roxann Dawson and written by Chris Black.