Picture it, Nazi occupied France, Gestapo headquarters, 1943. That’s where this week’s episode starts off. A Nazi officer has retrieved a box full of something his country has been looking for. He allows his french prisoner to take a peak in the box. Once she sees what's inside she quickly and easily kills the Nazi officer, revealing to him before his death that not only is she NOT a french traitor, but that she is working with the Men of Letters. She makes her way off with the box.
Back at the bunker, Sam and Dean have run out of coffee. Something I suppose does not matter in the scheme of the episode, but man, that sucks when you run out of coffee.
Anyhow, Sam has been dabbling in some general biblical/historical stuff including Nazis, to see if he can find some other way to fight Amara. He explains to Dean that the Nazis once studied archeology (which anyone who has seen Indiana Jones, KNOWS). One of the items that the Nazis most wanted to obtain was a box full of items that had been touched by God collectively know as, “The Hand Of God”. The power they contained would have enabled the Nazi’s to win the war. What Sam and Dean discover is that the Nazi’s DID find the Hand of God, but that it had been stolen by Dalphine, a Woman Of Letters. As it turns out Dalphine had attempted to bring the treasure from France straight back to the bunker, but the sub she hitched a ride on was attacked by Germans and sank.
In hell a very bored Cassifer has established himself as the King of Hell and is killing time playing angry birds. And also being very uninterested in the updates from Crowley’s minions, who have thrown all their loyalty towards Lucifer. Lucifer is keeping Crowley, chained up as his pet dog. Crowley seems to have given in and is loyal to his “master”
But Lucifer gets Crowley to admit he’s only biding his time until he sees his chance to get his throne back. And admits that maybe taking out Amara was to be more of a group effort than he had anticipated… Just then Cassifer gets a call from Dean that they need his help.
Cassifer arrives at bunker where the boys explains about the Hand of God (still thinking it’s Cas) and it is suggested that he send the boys back in time to retrieve the box right before the sub is sunk. Sam ask Cas about the risks, who is not very concerned. Dean tells Sam it's the only way and that he needs to stay put at the bunker in case things get sideways so someone will still be there to take on Amara. Cassifer promises Sam that he’ll never let Dean out of his sight and off they go. Next thing Dean knows he’s on the ship, with no Cassifer in sight. Dean hides out in beneath a bunk.
Back at the bunker a soaking wet Cassifer shows back up. He was able to get Dean on the ship but, he fell short because the ship must have had some sort of warning from Dalphine. Sure from beneath the bunk Dean sees a sigil low on the wall. Realizing Cas won't be able to get on the ship, he tackles one of the men and takes his shirt in hopes he can find Dalphine. Dean is quickly caught and confesses the truth to Dalphine, the Captain and a couple of other men on the sub, who don’t believe him. Dean explains to Dalphine that she needs to clear the sigils, so he can get the weapon to safety and use it in the war he is fighting in the future. She believes him and tells him that she trusts him. Just then the German sub is spotted.
Back at the bunker Sam finds a spell that can clear the warding from the outside but it takes an archangel, which Cas is not… but Lucifer. Sam leaves the room and when he returns Cassifer is cooking up the spell. When he tries to convince Sam that he will be able to make it work, Sam offers up his soul to help give “Cas” enough power. With that, Cassifer begins to laugh and can’t keep it any longer.
Sam begins to put it together that it’s not Cas, but Lucifer. Not a moment too soon, as Lucifer realizes he has no need to keep Sam alive and that having to use “his soul to save Dean” is the perfect cover story to tell Dean. Lucifer reaches into Sam’s soul but before he can kill him Cas finally begins to surface and fights Lucifer back. Cas quickly explains to Sam why he said yes to Lucifer and that no matter what, they need Lucifer to save Dean, because Cas can’t.
Back in 1943, Dalphine clears off the warding one, which is embedded into her body. The only way to get rid of it is to kill her.
Dean hesitates, but before he can make a choice,
the bombing begins. Then instead of finishing them off, the Germans send a message - it’s Dalphine’s boyfriend from earlier, he is one the Nazi necromancers (see “Everybody Hates Hitler” from Season 8). The Germans offer, in return for Dalphine and the box, to spare the lives of the men on the sub and send them to a POW camp. There is no discussion on the ship - it's not an option. Instead Dalphine uses the hand of God to destroy the German sub. The damage to their sub is already enough to sink them - but before then Cassifer shows up and brings Dean back to the bunker. The first thing out of Sam’s mouth is that Cas is Lucifer!
Lucifer smiles, “Cats out!” Cas explains the torture of “being Cas” and happily unwraps the Hand of God, only to find it doesn’t work. It was a one time shot and Dalphine already used it up. Before Lucifer can kill them, Sam wards him away with that bloodied symbol we haven’t seen in many a season...
Later, reflecting on the day Dean tells Sam now they need to hunt Lucifer and save Cas, and refuses to believe Cas chose to say yes. Dean is troubled by the loss he saw on the ship; he explains that he did nothing on the ship, he was just a witness.