What does Rhysand realize has happened to Nesta, Gwyn, and Emerie in Chapter 63?

Rhysand and Cassian go to Windhaven where Nesta and Gwyn have spent the night with Emerie. When they arrive at Emerie's place, they see that each of the females had fought and was hurt. Rhysand contacts Devlon and he realizes that Nesta, Gwyn, and Emerie were snatched from their beds to participate in the Blood Rite