Spike has been one of my absolute characters ever since his very first appearance in season two. This episode was a gift to me.
When Buffy gets hurt on patrol, she becomes more aware of her mortality in the everyday. She interrogates Spike on his unlife and how he got two slayers under his belt.
His story is told in flashbacks, starting from his turning, and showing pivotal points in his vampiric life and how he became the man he is today.
We see that Spike started out as the shy poet William, who got his infamous nickname as part of 'William the Bloody Awful Poet'. He is spurned by his ladylove, an upper class snob. He leaves in tears and runs into Drusilla. The scene is part of the B side of a crossover scene with Angel's 'Darla' episode. Then Angelus sparks his interest in slayers while William picks up a rougher working class accent. His fight with his first slayer is shown at the Boxer Rebellion, during which he acquires his eyebrow scar. He kills her, obviously. Then again, in 1977 New York, he fights his second slayer in a subway. He is full on punk by now, with the bleached blond hair we know so well. He kills this slayer not by drinking her, but by breaking her neck and taking her black coat as a trophy.
These scenes are intercut with Spike's interactions with Buffy. They take the scene outside to the alley, where Buffy rejects Spike's advance, repeating to him the words that ended his life, "You're beneath me." Enraged, he determines to kill her, but seeing her on the back porch of her home, crying at the news of her mother's hospitalization, he sits down next to her and comforts her.
This episode is not perfect, and most of the beginning up to where Spike comes in bores me, but it is definitely one of my all time favorite episodes. I recommend this to all newcomers.