I found the place. Thirty-nine steps , I read, and again, thirty-nine steps⁠—I counted them⁠—high tide 10:17 p.m.

The Admiralty man was looking at me as if he thought I had gone mad.

“Don’t you see it’s a clue,” I shouted. “Scudder knew where these fellows laired⁠—he knew where they were going to leave the country, though he kept the name to himself. Tomorrow was the day, and it was some place where high tide was at 10:17.”

“They may have gone tonight,” someone said.

“Not they. They have their own snug secret way, and they won’t be hurried. I know Germans, and they are mad about working to a plan. Where the devil can I get a book of tide tables?”

Whittaker brightened up. “It’s a chance,” he said. “Let’s go over to the Admiralty.”

We got into two of the waiting motorcars⁠—all but Sir Walter, who went off to Scotland Yard⁠—to “mobilize MacGillivray,” so he said. We marched through empty corridors and big bare chambers where the charwomen were busy, till we reached a little room lined with books and maps. A resident clerk was unearthed, who presently fetched from the library the Admiralty Tide Tables. I sat at the desk and the others stood round, for somehow or other I had got charge of this expedition.

It was no good. There were hundreds of entries, and so far as I could see 10:17 might cover fifty places. We had to find some way of narrowing the possibilities.

I took my head in my hands and thought. There must be some way of reading this riddle. What did Scudder mean by steps? I thought of dock steps, but if he had meant that I didn’t think he would have mentioned the number. It must be some place where there were several staircases, and one marked out from the others by having thirty-nine steps.