Then Garth suggested that we should take Custrin as well.
"Capital fellow, the doctor," he remarked, "what the Americans call a good mixer. I like Custrin. And he'll be useful, you know, Okewood, in the case of snake-bite or anything like that, eh?"
Now, as I have explained, I hadn't particularly cottoned to Custrin. Since that first night out he had made famous progress with Marjorie and while Garth and I were sweltering in the hold, assembling equipment and supplies for our expedition, she and the doctor had sat for hours at the piano in the saloon. I have always tried to be honest with myself and I may as well admit that I was envious of Custrin's delightfully easy manner. He was never gauche or sheepish with Marjorie and I knew what a boor she had set me down in her estimation.
So I demurred from the proposal of Sir Alexander. The party was big enough, I urged; to add another mouth would mean seriously increasing the amount of supplies we should have to take with us.
"But Custrin's a first-class geologist as well," pleaded the baronet, "and his knowledge should prove most valuable in our quest!"
I felt a very unpleasant suspicion dawn within me. Was it possible that Garth had told Custrin about the grave on the island and the clue that lay in my letter-case?
"Have you told Custrin about the treasure?" I asked bluntly.
Garth looked decidedly uncomfortable.
"The doctor's a most reliable fellow and highly recommended, very highly recommended to me. You can see his references if you wish, major. He is quite one of us, you know, and I did not think there was any harm.... Really, I think he'd be a distinct asset. Besides, he'll be horribly disappointed now if we don't take him!"
Then, of course, I knew that Garth had told Custrin the whole story and had definitely promised him into the bargain that he should join our party. I remembered now that the two had been in the smoke-room alone together for an hour or more after lunch. I breathed a little prayer of thanksgiving that in my almost wholly Irish nature a little store, an isolated stronghold, as it were, of caution, legacy of some unknown ancestor, was included. Throughout my career in the Secret Service I have made it a practice, when disclosure is necessary, to disclose only as much as is absolutely essential to the business in hand. My brother Francis, probably the greatest secret agent our country has ever had, gave me this tip.