On the backs of many of them were strange luminous designs, crosses, spots, circles, and straight lines. These marks could be distinctly seen with the aid of the smoked glasses. Lifting his hand, Merry raised the glasses. The glowing marks vanished! A feeling of satisfaction shot through the discoverer. “I have him!” he mentally exclaimed. “I have detected his clever little trick!” It happened that Darleton received a pair of jacks and a pair of sixes on the deal. One of the players “stayed” and Darleton “came up.” On the draw Darleton caught another six spot, giving him a full hand. He seemed to be looking at his cards intently, but Frank observed that he had watched every card as it was dealt. In the betting that followed Darleton pressed it every time. At the call he displayed the winning hand. But just as he reached to pull in the chips his wrist was clutched by a grip of iron. Frank Merriwell had grasped and checked him. “Gentlemen,” cried Merry, “you are playing with a crook! You are being cheated!” Instantly there was a great stir in the room. Men sprang up from their chairs. Darleton uttered an exclamation of fury. “What do you mean, you duffer?” he snarled. “Let go!” Instead of obeying, Merry pinned him fast in his chair, so he could not move. “Yes, what do you mean?” shouted one of Darleton’s friends, leaping from another table and endeavoring to reach Frank. “Let go, or I’ll——” Hugh Morton grappled with the fellow. “I wouldn’t do anything if I were you,” he said. “Take it easy, Higgins. We’ll find out what he means in a minute.” “Find out!” roared Higgins. “You bet! He’ll get all that’s coming to him for this!” “Explain yourself, Mr. Merriwell,” urged one of the players. “This is a very grave charge. If you cannot substantiate it——” “I can, sir.” “Do so at once.” “These cards are marked.” “It’s a lie!” raged Darleton. “You must prove that the cards are marked, Mr. Merriwell,” said another player. “They were but lately unsealed, and it seems impossible.” “They have been marked since they were opened.” “How?” “With the aid of luminous marking fluid of some sort, carried in this man’s pocket. I have watched him marking them.” “Liar!” came from the fellow accused; but he choked over the word, and he was white to the lips, for he had discovered that Merry was wearing smoked goggles, like his own. “Let me get at him!” panted Darleton’s friend; but Morton continued, with the assistance of another man, to hold the fellow in check.