The sandy-haired man did look sharp; and within three minutes we were driving off with our tickets to Prince’s Dock landing-stage.

We slipped on board unobtrusively, and instantly took refuge in our respective staterooms till the steamer was well under way, and fairly out of sight of Kolaba Island.  Only after all chance of Sebastian’s avoiding us was gone for ever did we venture up on deck, on purpose to confront him.

It was one of those delicious balmy evenings which one gets only at sea and in the warmer latitudes.  The sky was alive with myriads of twinkling and palpitating stars, which seemed to come and go, like sparks on a fire-back, as one gazed upward into the vast depths and tried to place them.  They played hide-and-seek with one another and with the innumerable meteors which shot recklessly every now and again across the field of the firmament, leaving momentary furrows of light behind them.  Beneath, the sea sparkled almost like the sky, for every turn of the screw churned up the scintillating phosphorescence in the water, so that countless little jets of living fire seemed to flash and die away at the summit of every wavelet.  A tall, spare man in a picturesque cloak, and with long, lank, white hair, leant over the taffrail, gazing at the numberless flashing lights of the surface.  As he gazed, he talked on in his clear, rapt voice to a stranger by his side.  The voice and the ring of enthusiasm were unmistakable.  “Oh, no,” he was saying, as we stole up behind him, “that hypothesis, I venture to assert, is no longer tenable by the light of recent researches.  Death and decay have nothing to do directly with the phosphorescence of the sea, though they have a little indirectly.  The light is due in the main to numerous minute living organisms, most of them bacilli, on which I once made several close observations and crucial experiments.  They possess organs which may be regarded as miniature bull’s-eye lanterns.  And these organs—­”

“What a lovely evening, Hubert!” Hilda said to me, in an apparently unconcerned voice, as the Professor reached this point in his exposition.

Sebastian’s voice quavered and stammered for a moment.  He tried just at first to continue and complete his sentence:  “And these organs,” he went on, aimlessly, “these bull’s-eyes that I spoke about, are so arranged—­so arranged—­I was speaking on the subject of crustaceans, I think—­crustaceans so arranged—­” then he broke down utterly and turned sharply round to me.  He did not look at Hilda—­I think he did not dare; but he faced me with his head down and his long, thin neck protruded, eyeing me from under those overhanging, penthouse brows of his.  “You sneak!” he cried, passionately.  “You sneak!  You have dogged me by false pretences.  You have lied to bring this about!  You have come aboard under a false name—­you and your accomplice!”