As the Enterprise embarks on yet another humanitarian mission to stop yet another deadly plague, a strange and unexpected thing happens in mid-journey: Counselor Troi announces she's pregnant. "Who's the father?" Riker asks accusingly. "There is none," Troi responds.
The height of this episode's wit comes with a funny-in-its-savageness remark by Worf, whose utterly pragmatic Klingon-security-officer response to this mysterious, alien-influenced immaculate conception is simply that it must be terminated at once in order to wall off all possible risk. (Just think of how this could've been the ultimate launching-off point for an abortion-debate episode. Never mind.) The story's sci-fi gimmick is that the pregnancy proceeds at a vastly accelerated rate, such that Troi is giving birth to a son named Ian by the second act. The baby's accelerated growth proceeds from there, and Ian is an eight-year-old boy within 24 hours.
The problem with this story is that it has far too little curiosity in Ian or Troi (for most of the episode, their mother/son scenes meander with precious little original insight or interest), and far too much curiosity in the technobabble subplot, involving a deadly substance sealed in a container for transport to another facility. Some mysterious radiation is causing the seal to crack; if the substance gets out, everyone on the ship will die. The tedious tech details of the radiation, the leak, and the resulting threat drag on needlessly long, causing all interest to drain from the story.
And what about Ian? The story doesn't deal with him nearly enough, until the closing scenes where we learn he's the source of the mysterious radiation, and that he was born to Troi to learn about the human life cycle. Ian's self-sacrifice (or a reversion to his true energy state, if that's the same thing) makes for a good emotional scene that Marina Sirtis delivers on, but the sci-fi themes are familiar.
The episode's serviceable supporting material surrounds Wesley's question of whether to join his recently reassigned mother at Starfleet Medical, the introduction of the abrasive new McCoy-wannabe Dr. Katherine Pulaski (Diana Muldaur), and Guinan (Whoopi Goldberg) as the bartender of Ten-Forward, the Enterprise's new (or at least previously unseen) refreshment lounge.