I'm kinda disappointed that they took out parts of the novel :( I wonder if they'll ever show the part with the necklace.
For the necklace,
Notice how it disappeared when the maid walked in? Edith warned the guy to run away and sell her necklace (by memory, she wanted to thank him that way).
More
Spoilers ahead
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When Killian is on the search for Edith, he comes across the guy that helped Edith. Killian interrogated him about the necklace, and I believe that's how Killian knew Edith was with his mother and Rhyse, despite Cliff's claims
Spoiler
Sophia and Edith's brother were being captured by Cliff's troupes... Because Sophia (the mercenary maid who tortured Edith since she was a child) is very petty she didn't wanted Edith to be rescued from Cliff's men (or Edith having an Happy Ending).
When Cliff asked where was Edith to Sophia (because he remembered her as Edith's maid), Sophia pretended to admit Edith's treason to the Rudwick by telling lies to Cliff such as Edith betrayed them and that she was on Rigeloff's side. Sophia was also the one who said that a place like where they are now was not appropriate for a noble Lady as Edith so Edith couldn't possibly be there...
Cliff believed such blatant lies because before that, when Cliff was still in the battlefield, Lize once reported in her letters to Cliff... Edith's strange behavior. Cliff showed this letter to his father the Duke and both believed Lize for sure... That's why Cliff was ordered to return to the capital. And because they couldn't find Edith in the manor, Cliff decided that Sophia told him the truth even though he was clearly biased so his judgment couldn't possibly grasp the whole picture of the situation...!
That's also why I can't bring myself to appreciate the Duke (Killian and Cliff's father)... Like Killian have a say in this but the Duke deliberately hid the truth to Killian because of their biased judgment!?
Killian had to suffer so much because of his brother and Father that it's insane. I feel very bad for Edith and Killian because of that.
We should all just die