Soldiers of Fortune by Richard Harding Davis

Clay and Langham left MacWilliams and Stuart to look after their prisoner, and returned to the Palms, where they dined in state, and made no reference, while the women were present, to the events of the day.

The moon rose late that night, and as Hope watched it, from where she sat at the dinner-table facing the open windows, she saw the figure of a man standing outlined in silhouette upon the edge of the cliff. He was dressed in the uniform of a sailor, and the moonlight played along the barrel of a rifle upon which he leaned, motionless and menacing, like a sentry on a rampart.