I'm confused(Spoilers)

[Samoht]

So I just past the part in the prison where you rescue Mary and Anne. While I was doing the side objectives i noticed it was Vane in de prison... But didn't Edward kill him on that island they stranded on? Was it a memory of him in that cell?
I don't understand :(

[Ashmedai]

No, Edward just wounded Vane when they were marooned on the island. He was later captured by the British, and hanged at some point after Edward escaped for the prison.