I found this plot to be a little strange, but not hard to follow. The Enterprise must investigate the destruction of a colony and why only there only seem to be two survivors.
Its a basic tale of morals and ethics and the emotions and changes they imprint on us. Furthermore, the notion of what constitutes a crime is brought up in the quintecessital ST way. The ambiguity of what classifies such an act is demonstrated by the powerful yet singluar eternal being that takes the guise of the old man who came to human colony, fell in love with a human female and then did nothing because of his ethical reasoning to defend it from an unwinable attack.
The consequences of such an action and the beings peculiar behaviour is the main flow of entertainment throughout this 45mins. There is little action involved as this episode is more of your common garden variety mystery which must be dispelled by the crew as they peel away one layer at a time, to reveal the secret of what is going on.
Several well conceived clues gradually garner the reality of what is going, the strongest being what begins to happen to Deanna.
The pace throughout the first two acts is slow, but it does hot up somewhat towards the end, when the crew discover the true identities of both so-called survivors.
Its a shame that this being wasnt incorporated into other future storylines, but the episode is logically constructed and is extremely watchable.