The Thirty-nine Steps
By John Buchan
Public Domain Books
(1) Place where there are several sets of stairs; one that matters distinguished by having thirty-nine steps.
(2) Full tide at 10.17 p.m. Leaving shore only possible at full tide.
(3) Steps not dock steps, and so place probably not harbour.
(4) No regular night steamer at 10.17. Means of transport must be tramp (unlikely), yacht, or fishing-boat.
There my reasoning stopped. I made another list, which I headed ’Guessed’, but I was just as sure of the one as the other.