The Doctor narrowed his eyes and looked towards the Ferris wheel, he didn't believe it "How do you know and who are you!" He was getting a little angry now. He wasn't sure if he was been lied or not. He wasn't even sure Arwen would know who she was if that was true, she acted like she had only just met him "She didn't even know who I was till now."
He was worried for her safety still, he was thinking deeply. He knew there would be a problem if she was his sister and didn't know. How could he even tell her that.