It was just a little private bit of romance and adventure for Mark, three days ago. He didn't even know that Robert was coming. But somehow the passage has been used since, in connection with Robert. Perhaps Mark escaped that way; perhaps he's hiding there now. And if so, then the only person who could give him away was Miss Norris. And she of course would only do it innocently not knowing that the passage had anything to do with it."
"So it was safer to have her out of the way?"
"Yes."
"But, look here, Tony, why do you want to bother about this end of it? We can always get in at the bowling-green end."
"I know, but if we do that we shall have to do it openly. It will mean breaking open the box, and letting Cayley know that we've done it. You see, Bill, if we don't find anything out for ourselves in the next day or two, we've got to tell the police what we have found out, and then they can explore the passage for themselves. But I don't want to do that yet."
"Rather not."
"So we've got to carry on secretly for a bit. It's the only way." He smiled and added, "And it's much more fun."
"Rather!" Bill chuckled to himself.
"Very well. Where does the secret passage begin?"
