"Delighted--in both instances. My compliments, Sir Henry. By any chance that Sir Henry Wilding whose mare, Black Riot, is the favourite for next Wednesday's Derby?" "Yes--that very man, Mr. Cleek; and if--" "Don't get excited and don't turn, please; our friend the policeman is looking this way. What's the case? One of 'nobbling'? Somebody trying to get at the mare?" "Yes. A desperate 'somebody,' who doesn't stop even at murder. A very devil incarnate who seems to possess the power of invisibility, and who strikes in the dark. Save me, Mr. Cleek! All I've got in the world is at stake, and if anything happens to Black Riot, I'm a ruined man." "Yar-r-r!" yawned the elderly sea captain, rising and stretching. "I do believe, constable, I've been asleep. Warm weather, this, for May. A glorious week for Epsom. Shan't see you to-morrow, I'm afraid. Perhaps shan't see you until Thursday. Here, take that, my lad, and have half-a-crown's worth on Black Riot for the Derby; she'll win it, sure." "Thanky, sir. Good luck to you, sir." "Same to you, my lad. Good day." Then the old gentleman in the top hat and white spats moved slowly away, passed down the tree-shaded walk, passed the romping children, passed the Princess Louise's statue of Queen Victoria, and, after a moment, vanished. Ten minutes later, when Narkom and Sir Henry returned to the waiting motor, they found him seated within it awaiting them, as he had promised. Giving Lennard orders to drive about slowly in the least frequented quarters, while they talked, the superintendent got in with Sir Henry, and opened fire on the "case" without further delay.