I liked this episode far better than the first two. I thought it was proper Star Trek. Back to the original series or TNG. A classic science fiction mystery story!The U.S.S. Enterprise encounters a contagion that ravages the ship; one by one, the entire crew is incapacitated except for Number One, Una Chin-Riley, who must now confront a secret she's been hiding as she races to find a cure.
Like last week, this episode focussed the character building on just two crew. This week it was Doctor M'Benga and Number One. Doctor M'Benga secretly keeps his daughter in the Sickbay medical transporter pattern buffer. I had a problem with that transporter when it was first retconned because Scotty had to move mountains to site-to-site transport to Sickbay. Now that M'Benga holds someone in the pattern buffer, when only Scotty can do that, when he performs a miracle to save his own life (Relics, TNG). Sorry, I will never like this as it makes Scotty's miracles into everyday tasks. Otherwise it was a good story.
We find out that number One is an Augmented genetically altered human and that La'an Noonian Singh is an ancestor of Khan. This idea of Number one having something to hide makes sense on many different levels. It explains why "the best second officer in Starfleet" isn't promoted to Captain (rather than because she was a female in the 1960's).
However, it did run into some terrible technobabble and some real wackiness in the final third of the episode.