If you sit back and think about it this episode is pretty much is the Empire Strikes Back of Unlimited Blade Works. You have a protagonist who came in to rescue a friend while not being fully trained and was consequentially humbled by his lack of experience. In the process of that botched rescue attempt the protagonist is gravely injured physically and emotionally. Secrets are exposed about the origin of the protagonist which change the way people look at him. You have a hero left in the grasp of the enemy with their future looking quite grim. You have the villains triumphant with their end goals now within sight. The heroes still have a chance to strike back but they are clearly on the defensive and have nearly depleted their moral. All hope seems lost and it will take a mixture of clever planning and a few well-timed miracles for them to succeed.
Although Archer is much more the morally gray scoundrel than Saber it is all fairly analogous. But such are the limits of analogies. They are far better at hinting towards ideas then being one to one representations. But the similarities are still fairly striking. They are both clearly working on a Campbellian monomyth structure. The characters have entered the abyss. Part two of the series with be the death and rebirth of the hero. But before that transformation can occur the protagonist must be brought down to his lowest point in the series.
That is this episode.
Reverse Thieves 