Eurystheus did not know that in giving these tasks he was making his cousin fulfil his course; but he was afraid of such a mighty man, and hoped that one of these would be the means of getting rid of him. So when he saw Hercules at Argos, with a club made of a forest-tree in his hand, and clad in the skin of a lion which he had slain, Eurystheus bade him go and kill a far more terrible lion, of giant brood, and with a skin that could not be pierced, which dwelt in the valley of Nemea. The fight was a terrible one; the lion could not be wounded, and Hercules was forced to grapple with it and strangle it in his arms. He lost a finger in the struggle, but at last the beast died in his grasp, and he carried it on his back to Argos, where Eurystheus was so much frightened at the grim sight that he fled away to hide himself, and commanded Hercules not to bring his monsters within the gates of the city. There was a second labor ready for Hercules--namely, the destroying a serpent with nine heads, called Hydra, whose lair was the marsh of Lerna. Hercules went to the battle, and managed to crush one head with his club, but that moment two sprang up in its place; moreover, a huge crab came out of the swamp and began to pinch his heels. Still he did not lose heart, but, calling his friend Iolaus, he bade him take a firebrand and burn the necks as fast as he cut off the heads; and thus at last they killed the creature, and Hercules dipped his arrows in its poisonous blood, so that their least wound became fatal. Eurystheus said that it had not been a fair victory, since Hercules had been helped, and Juno put the crab into the skies as the constellation Cancer; while a labor to patience was next devised for Hercules--namely, the chasing of the Arcadian stag, which was sacred to Diana, and had golden horns and brazen hoofs. Hercules hunted it up hill and down dale for a whole year, and when at last he caught it, he got into trouble with Apollo and Diana about it, and had hard work to appease them; but he did so at last; and for his fourth labor was sent to catch alive a horrid wild boar on Mount Erymanthus. He followed the beast through a deep swamp, caught it in a net, and brought it to Mycenae.