This is absolutely one of the best episodes of Doctor Who ever made, and at its core, it is very simple. It is the triumph of love and compassion over hate and evil, and told in such a beautiful way. The Doctor is on Satellite Five with Jack mounting a suicidal defense against the Daleks. The Daleks are somehow worse than ever, they are self-hating religious zealots who kill for no reason other than sadism. When you look at the world today, how many people wish they could exterminate anyone unlike them? Then Rose is back home in London, completely failing to live an ordinary life. The Doctor taught her a different way to live, to be brave and confront evil. The choice is given to the Doctor again: all of humanity as collateral damage with the destruction of the Daleks. He chooses "coward every time", but his effect and kindness on others is rewarded by Rose arriving and cleansing the Daleks. Everyone is great, from Lynda with a y's horrific silent extermination death, Jack's glee in the defense knowing he dies, Jackie's reaction to Rose saying she was there when Pete died. This is a marvelous episode, and I think only The Doctor Falls has it beat in terms of finales. What both episodes have in common is that it isn't about winning a victory at any costs: it's about fighting for what's right even if the universe is against you. Bravo Doctor.