The discussion of their plans for the day occupied the rest of the meal. They had a whole twenty-four hours before them, for the _Ithuriel_ would not be back from San Francisco, where she was going when she passed the train, until ten o’clock on the following morning, so it was arranged that they would begin the day with a sleigh drive--a luxury which not even Aeria could afford,--then the two Aerians were to see the sights of the city under the guidance of Olga and Serge, and perform the chief of the duties that brought them to St. Petersburg. After luncheon they were to have a couple of hours on the ice in the park, into which the Yusupoff Gardens of the nineteenth century had been expanded, after which they would see the ice palaces illuminated at dusk, then dine, and finish the day at the opera. When the air-ship arrived, a rapid flight was to be taken across Europe over the Alps and back to Moscow, across Italy, Greece, and the Black Sea, which would enable Alan and Alexis to deposit their guests with their Moscow friends soon after nightfall. The sleigh drive took the form of a race, on the plain stretching towards Lake Ladoga, between the two troikas driven by Serge and Olga, who had so managed matters that she had Alan for a companion, and who, not a little to Serge’s disgust, won it, after a desperate struggle, by a head. The race was a revelation to the two Aerians, and when Alan handed Olga out of the sleigh after they had trotted quietly back to the city, the interest which she had excited in him during the railway journey had already begun to deepen into a sentiment much more pleasing and dangerous. The rest of the morning was devoted to driving about the city, and to paying a visit to the ancient fortress of Peter and Paul, which alone of all the fortress prisons of Russia had been preserved intact as a fitting monument of fallen despotism and a warning to all future generations. Once at least in his life every man in Aeria visited this fortress, as good Moslems visit Mecca, and this was the duty which Alan and Alexis were now performing. In one of the horrible dungeons deep down in the foundations of the fortress, under the waters of the Neva, they were shown a massive gold plate riveted on to the rough, damp, stone wall. Its surface was kept brightly polished, and it looked strangely incongruous with the gloom and squalor of the cell. On it stood an inscription in platinum letters let into the gold: “_In this cell Israel di Murska, afterwards known as Natas, the Master of the Terror, was imprisoned in the year 1881, previous to his exile to Siberia by order of Alexander Romanoff the last of the Tyrants of Russia._”