Who arrives after Harry gets back through the gap, what does Harry learn from Jack at that arrival and what does the person who comes say to Harry?

Richard arrives, and embraces his sister warmly. When Jack jokes about throwing away his career to join them, Harry is suddenly aware that Jack and the rest of his men have violated their regulations. Richard admits that he thought Father had told Harry about their Hill blood, and he is surprised to learn she became a Rider without being aware of her heritage. He pledges his loyalty to her.