Enterprise gives asylum to a Romulan defector.
This is a classic episode that has an excellent story and a number of great character moments.
The plot works on a number of levels, presenting aspects of a political thriller alongside a focus on command responsibilities in a volatile conflict situation. There is an inspiration from the Cuban missile crisis, some nice tributes to Shakespeare's Henry V and a clear anti-war message.
I cannot go into detail without spoiling key areas of the plot, but it's safe to say that the opening holodeck sequence sets the tone for what is to come and every character exchange that follows is memorable. Picard, Riker, Data, Worf and all the Romulan characters have many strong scenes of dialogue and for me it has one of the most effective endings to a Star Trek show.
'The Defector' is one of the definitive Romulan episodes and thoroughly establishes their deceptive nature and desire for conquest, whilst at the same time adding layers of depth with the portrayal of the title character.
Visually it works well with a number of nicely filmed sequences. The opening scene in particular is very atmospheric. Everything is edited in a way to keep the pace ticking over in an interesting way, especially with so much dialogue.
All performances are great with Patrick Stewart leading the cast brilliantly with great support by Brent Spiner, Jonathan Frakes, Michael Dorn and LeVar Burton. Andreas Katsulas has another excellent cameo. The star of the show though is guest actor James Sloyan with a fantastic turn as the defector.
This for me is the first Star Trek episode to compare favourably to the similarly themed original series classic 'The Balance Of Terror'.
There are some minor plot holes but nothing that distracts from the entertainment, so I think it's a 9.5/10 and round upwards.