Francesco had not seen the last of the French prisoners. In the summer of 1399, Boucicault, sent by Charles VI to assist Manuel II in defending Constantinople from the Turks, arrived at Lesbos, which he had last visited two years before. Francesco received him with outward signs of joy, but told him that he had already informed the Turks of this new expedition, as he was bound to do by the treaties which he had with them. The position of the Lesbian lord was, indeed, of no small difficulty. It was his interest to stand well with Bayezid, while his son-in-law, John Palaiologos, who spent much of his time in the island, had received, as the son of Manuel’s elder brother, Turkish assistance in his blockade of the Imperial city. The diplomatic Levantine did not, however, wish to offend his powerful guest; he therefore offered to accompany him, and ordered a galley to be made ready to join the expedition. But the information which he had supplied to Bayezid had put the Turks upon their guard. A raid in Asia Minor was Boucicault’s sole military success; but he achieved, probably thanks to the influence of Francesco, the reconciliation of Manuel with his nephew, whom the French Marshal fetched from Selymbria to Constantinople. Manuel then departed with Boucicault to seek aid at the courts of Europe, while John acted as his viceroy on the Bosporos and received, in the presence of the Marshal, the promise of Salonika as his future residence[550]. Thus, during the absence of Manuel, Francesco’s daughter Eugenia sat upon the Byzantine throne as the consort of the Emperor’s representative, while her sister Helene married Stephen Lazarevich, Despot of Serbia, who had made her acquaintance during a visit to Lesbos on his return from the stricken field of Angora[551]. Francesco was at that time holding Foglia Vecchia on a lease from the _maona_ of Chios, and his tact and presents saved the place in that crisis from the covetous hands of the victorious Timour and his grandson[552].