What sort of welcome had he received from M. Heberlauf? How had the arrest of Fantomas been effected? How had the monster died? The detective, naturally, had no intention of enlightening Wulf as to the truth. He therefore answered in monosyllables, annoyed by the turn the conversation had taken. In fact, as the questions became more pressing, it flashed through Juve's mind that the stupid officer was actually beginning to suspect him of being Fantomas. As the taxi neared its destination Juve suddenly put his head out of the window and cried with an oath to the chauffeur: "Follow that automobile which is just starting and don't lose sight of it!" Wulf turned inquiringly: "It's the Marquis de Serac." "Well, what of it?" "Why, is he the man we are after?" Then turning again to the chauffeur: "Have you plenty of gasoline?" "Enough to run a hundred miles, Monsieur." The chase began at the Boulevard de Courcelles, continued through the Place de l'Etoile and the Avenue de la Grande Armee. The two taxis, of the same horsepower, kept an equal pace, but the Marquis de Serac's chauffeur seemed the smarter man. At any rate, he was the more daring. He dodged in and out of the traffic and began to gain on his pursuers. "He's taking us to the Bois," growled Juve, as they made a turn to the left after passing the fortifications, before the Barriere de Neuilly. The pace increased in the back streets and then, suddenly, the taxi of the Marquis de Serac disappeared! It had turned sharply down a narrow street. At the risk of his neck, the detective sprang out of his taxi and rushed round the corner, just in time to hear a door bang to. Wulf now joined him. "We have wasted our time, my dear Juve. The taxi we have been following was empty. It made a circuit and passed me just now." "Just what I expected!" cried Juve, "our man got out of it ... he is still here." Juve took out his revolver, and then an exclamation of surprise escaped his lips. Fifty yards away, a figure appeared, vague and dressed in white. "What the devil does that mean? I've been following the Marquis de Serac, of that I'm sure, and now I find this other one." Then turning to Wulf, he gripped him by the arm. "You see that individual, well, he is the Primitive Man Ouaouaoua." * * * * * Taking the utmost precaution, Juve and Wulf followed the enigmatic Ouaouaoua for over an hour. The singular meeting had given the detective food for thought. This man had figured prominently at the ceremony of the Singing Fountains; again, he had been foremost in the demonstration of the mob against the King outside the Royal Palace. It was now that a suspicion came to Juve's mind, that this venerable beard and white woollen robe concealed the person of the Marquis de Serac.