As I was rewatching season one I noticed that Ethan admits to taking Clair and Charlie. Lock points out that he couldn't have taken them alone but there is only one set of foot prints and two drag marks. Echo had said that the others don't leave tracks there for he had the help of some one who is not an other to take Clair and Charlie. Later in the season Clair remembers that Danielle's scratches on her arm were caused by her. So did Danielle help Ethan take them in an attempt to get Alex back, she prived she was capable of that.
Just a thought.