Supergirl Season 4: 8 Ups & 2 Downs From 'O Brother, Where Art Thou?'

Contains spoilers from Supergirl Season 4, Episode 15.

To say that Supergirl's fourth season has leaned heavily on real-world issues would be quite the understatement. Hidden within the subtext of Agent Liberty's war on aliens, there is a message about the discrimination within our society and how certain higher powers can even encourage it. Take from that what you will but, with the villain still playing a prominent role, the show's political stance certainly isn't going anywhere any time soon. Having said that, it did take a back seat in this week's adventure, as a far more powerful enemy entered the fray.

There was a lot to unpack in 'O Brother, Where Art Thou'. On one hand, we finally saw the arrival of Superman's archenemy Lex Luthor, whose heavily-anticipated debut on the show promised to steer it into uncharted territory. On the other hand, we saw the fallout of last week's shock cliffhanger as Supergirl vet James Olsen fought for his life after being shot. Little did we know that the two events were more closely linked than we initially thought.

'O Brother, Where Art Thou' was a success on all fronts, introducing Lex Luthor in a way that remained relevant to the show while using the urgency of the current events to move the story forward in a major way. A classic example of Supergirl at its finest.

First, the positives.