The young warlock's surprise almost caused him to release the connection. But Gwen had no way of knowing that Merlin had witnessed the conversation. No, she was merely inquiring after his whereabouts.
Leon swallowed again, "He would have stayed with Arthur till the very end. The fact that he has not returned confirms our fears about the both of them."
This time Merlin purposefully severed the connection. They believed him dead. If he returned, the very sight of him would give them hope that Arthur was still alive. Merlin couldn't bear to bring such hope only to destroy it immediately.