True Confession time: Supernatural‘s story arc episodes tend to be my favorites, but I also find them to be the most difficult to commentate. I always feel like I have nothing to say about them. So, while I thought that “On the Head of a Pin” was a particularly strong and compelling entry for the series, I find I don’t have much to add beyond that. So here goes a straight plot summary.

The episode begins with Castiel on the scene of what looks to have been a major battle. Cars are strewn everywhere, alarms are blaring. He silences them with a swipe of his hand, and his attention focuses on a dead female angel. The battle between Good and Evil is not going well. 

Elsewhere, Sam and Dean are on the road, headed to Cheyenne to meet Ruby. Ruby has been tracking down leads, and although Dean is worn down and tired they are pressing onward. There is no rest to be had for them, however; they arrive at their motel room to find Uriel and Castiel awaiting them. The Angels advise Sam and Dean that seven of their kind have been murdered, and they need Dean’s help to torture the demon Alastair, captured at the conclusion of the prior episode, to glean from Alastair information about the killings. Dean doesn’t want to help, because it will mean revisiting the part of his life he most wants to put behind him, but he is not given an option by Uriel or Castiel. He’s whisked away, leaving Sam behind.

Dean is reunited with Alastair inside a nondescript building. Alastair is strung up on an Old Enochian devil’s trap constructed by Castiel himself. It’s an imposing-looking rack meant to be all business. Somewhat unfortunately, the trap features a Star of David and this episode aired the same week as the “Reaper” episode in which Sam (not to be confused with Sam Winchester) accidentally draws a pentagram using a Star of David, only to have the Devil tell him “Mazel Tov!” So I had a hard time taking the Old Enochian trap seriously. But, whatever. This trap is supposed to be strong enough to hold Alastair.

Dean pulls Castiel aside. Castiel tells Dean that his superiors have begun to question his sympathies – Castiel has begun to express emotions, and these “doorways to doubt” can impair judgment. Castiel tells Dean that he has no choice but to torture Alastair. Dean complies. He wheels in a cart loaded up with implements of torture.

Meanwhile, back at the hotel, Ruby arrives to see Sam. Sam confides to Ruby that he is worried about Dean. He’s not worried about Dean becoming a torturer again, though. He’s just worried that Dean doesn’t have it in him to do what needs to be done. It’s a pretty callous and surprising thing for Sam to say, though indicative of the direction Sam has been headed all season. He’s more concerned about the job getting done than he is about anything else – including his brother going through Hell again. He asks Ruby to help him locate Dean, so he can intervene and help do what he suspects Dean cannot. Ruby burns a map to reveal the needed location, and then helps Sam power-up by feeding him some of her blood – apparently not for the first time.

Back at the holding area, the torture of Alastair is getting underway. Alastair reveals to Dean that he tortured Sam and Dean’s father, John, for 100 years. Each day he gave John the same offer he gave to Dean, to become the torturer rather than the torturee, but John never accepted. Dean accepted after only 30 years. While Dean is torturing Alastair, a faucet mysteriously turns and water begins dripping onto the chalk-line of the trap.

Outside the torture room, fallen angel Anna Milton appears. She questions whether torture can really be the will of God. She asks Castiel to join her, to recognize his doubt over whether the ends justify the means. For the moment, he refuses.

Meanwhile, the torture of Alastair continues. Physically, Dean is pummeling Alastair. Psychologically, Alastair is winning. He tells Dean that the first time Dean tortured a soul in Hell, the first seal broke. This was the plan of the demons; to get a righteous man to spill blood in Hell. It was supposed to be John, but Dean worked in a pinch when John refused to cooperate. Dean doesn’t take the news that he started the Apocalypse well, and things quickly go from bad to worse as the dripping water has allowed Alastair to free himself of the trap. He quickly beats Dean down, and then battles Castiel. During the battle, Alastair admits that he does not know how to kill angels; he can only send them back to Heaven. Things are not looking good for Castiel, but Sam arrives just in the nick of time. He does what Dean could not. Within a few moments, he is able to torture information out of Alastair. Sam gets Alastair to admit that he does not know who is killing the angels, but that it is not demons. Sam reveals, to Castiel’s obvious surprise and to Alastair’s dismay, that he has become strong enough not just to send demons back to Hell but to kill them entirely. He kills Alastair.

The torture of Alastair concluded, Castiel and Uriel have a park bench talk. They acknowledge that they are losing the battle. Castiel questions the death of the angels, and posits that perhaps Heaven is killing angels to punish them for losing, but that this is not something God would do. Castiel wonders if perhaps God is not the one giving orders. Uriel declares that he is not going to wait to be gutted – he is going to fight. Uriel departs to seek revelation. Later in the evening, Castiel calls out to Anna. He tells her that he is considering disobedience, and he asks her for advice. She declines, telling him it is time for him to think for himself. From their conversation, it is obvious that before she fell, Anna led Castiel.

Castiel decides to think for himself. He investigates the failure of the Old Enochian trap, and discovers the leaky faucet. Based upon the fact that only an angel could have broken the trap, he concludes that the true culprit must be Uriel and he confronts him about it. Uriel explains that his plan was to have Alastair kill Dean and then escape, so that the demons would continue to be scapegoated for the murder of angels. Uriel tells Castiel that he is not murdering angels so much as he is “converting” them. He states that God stopped being their father the moment that he created humanity and started playing favorites. Uriel’s goal is to raise their brother, Lucifer, to have him help put an end to the blight that is humanity. Uriel asks Castiel for his help, but Castiel declines and an angelic throwdown ensues. Just as things are looking grim for Castiel, Anna intervenes. She stabs Uriel from behind, dispatching him.

The episode concludes with a conversation between Dean and Castiel. Dean is recouperating in the hospital from his fight with Alastair. He asks Castiel to confirm whether it is true that he broke the first seal, and Castiel acknowledges this to be true. Castiel tells Dean that the angels tried to reach Dean before he could do so, but they were too late. He also tells Dean that only he, who started the breaking of the seals, can end it. Dean despairs, telling Castiel he is too weak – that this is too big for him. He asks Castiel to find someone else. Even as he asks, he knows the fate of humanity turns on him. With that, the episode concludes.

This episode takes its title from the theological quandry “How many angels can dance on the head of a pin?” So, how many angels can dance on the head of a pin? I have no idea. But here’s someone who does.

At the risk of diluting the impact of the whole scoring system, I’m going to give this episode another perfect 5 out of 5 Metallicars.