In Strange Company by Guy Boothby

When, after leaving Papeete, Veneda came to consider the facts connected with his excursion ashore, he could not help seeing two things very clearly. In the first place, he was quite convinced in his own mind that, to obtain the information she wanted, Juanita had drugged the champagne he had drunk at lunch; but in the second, though he was loth to let her treachery pass unpunished, he could not but tell himself that it would be a most foolish proceeding on his part to allow her to suspect that he considered it of sufficient importance to make a fuss about. To confess annoyance would be to admit that the locket contained what she was in search of, and this he was, naturally, most anxious not to do. One thing was very certain, the situation was becoming more and more complicated every day; for each twenty-four hours was bringing them nearer to civilization, and once there the difficulties of his position would be intensified a hundred-fold.

If Juanita were really in collusion with the Albino, it was most imperative that she should be outwitted, and that within the next fortnight. But though he racked his brains day and night for a scheme, he could not hit upon one that was in any way likely to prove successful.