Imagine his wrath, therefore, when he saw the Immortals also retreat, after many useless efforts to drive away the enemy. The Persians did not know what to do. They could not advance, and were ashamed to retreat. LI. DEATH OF LEONIDAS. While the Persians were hesitating thus, a Greek shepherd, Eph-i-al'tes, stole into their camp, and, vile traitor that he was, offered to show them another way to get into Greece, if they would pay him well. This man was led into the tent of a Persian general, where he explained that he could easily lead a troop of Persians over the mountains. By a goat path known to the Greeks only, it was possible not only to cross the mountains, but also to come down upon the small Greek force guarding the Pass of Thermopylae. His offer as guide was accepted. Ephialtes, true to his promise, if not to his country, led the Persian Immortals along this narrow way. Leonidas, who could not imagine that any one of the Greeks would be base enough to sell his country and honor for gold, had placed only a few of the allies at this spot. [Illustration: A Fighting Persian.] The Immortals followed Ephialtes, easily cut these few men down, and came unperceived behind the Spartan troops. It was only when he heard the tramp of horses behind him and on the mountain above him, that Leonidas found out that he had been betrayed. Hastily calling his allies, he gave them permission to save themselves by flight, declaring, however, that he and his companions would never leave their post, and that, since they could not conquer, they were ready to die. Some of the allies took advantage of this permission to escape, but seven hundred Thes'pi-ans nobly chose to remain with the Spartans. With the courage of despair, these men now fought against the Persians before and behind them, selling their lives as dearly as possible. In spite of the odds against them, they refused to surrender, and finally fell, one after another, on the spot which they had undertaken to guard. Their bodies, which were found almost in a heap,--for they had scorned to fly,--were honorably buried in a single mound, over which rose a monument with this modest inscription,-- "Go, passer-by, at Sparta tell, Obedient to her law we fell." The Persians had forced their way into Greece. Nothing could check their further advance, so the mighty army swept southward. The first place of note on their way to Athens was Delphi, the site of the sacred temple, where great treasures were stored. The Greeks knew that the Persians did not worship the same gods, and feared that they might rob the temple: so they now eagerly questioned the oracle, to find out whether they should not all assemble there in its defense. To their surprise, the oracle proudly replied, "The gods will take care of their own," and bade them rather use their strength to defend their own homes.