I think Ragnar knew there was no way they had a chance when he saw Rollo standing there staring at Gisla, so he bailed. Even though they got over the wall, with Rollo more concerned with Gisla, it was a good idea to retreat.
That was weird with Bjorn, he sure looked dead when Ragnar found him. Yes, it was odd how Rollo stood there at the base of the tower the whole time as arrows killed everyone around him. Then he gets to the top of the wall, fully exposed, wiping out Parisian guards swinging his battle ax around, yet no arrow hits him. I thought that was corny.
My take on Ragnar/Floki is Ragnar is influenced by the Christianity of Athelstan and wanted to let Floki see for himself it isn't all about the gods blessing or condemning your actions.
I am worried about Ragnar and the coughing blood. He took a bad fall. It looks like everything is back to normal next week in the preview, so maybe Ragnar recovers from his damage.
Lagertha and Kalf? That was super awesome when she told him she was going to kill him at some point, but lets enjoy each other now.
-Mike