So Sir Gawaine rode quickly forth, and Gaheris his brother rode with him, instead of a squire, to do him service. As they followed the hart by the cry of the hounds, they came to a great river. The hart swam over, and they followed after, and so at length they chased him into a castle, where in the chief courtyard the dogs slew the hart before Sir Gawaine and young Gaheris came up. Right so there came a knight out of a room, with a sword drawn in his hand, and he slew two of the greyhounds even in the sight of Sir Gawaine, and the remnant he chased with his sword out of the castle. When he came back he said, "O my white hart, me repenteth that thou art dead, for my sovereign lady gave thee to me, and poorly have I kept thee. Thy death shall be dear bought, if I live." Anon he came fiercely towards Sir Gawaine, and they struck mightily together. They clove their shields and broke their helms and hauberks so that the blood ran down to their feet. At the last Sir Gawaine smote the knight so hard that he fell to the earth; and then he cried for mercy and yielded himself, and besought Sir Gawaine as he was a knight and gentleman to save his life. "Thou shalt die," said Sir Gawaine, "for slaying of my hounds." "I will make amends," said the knight, "unto my power." Sir Gawaine would no mercy have, but unlaced his helm to strike off his head, when at that instant came his lady out of a chamber. She fell upon her husband just as the blow descended, and so Sir Gawaine smote off her head by misadventure, and the knight was saved. "Alas!" said Gaheris, "that is foul and shamefully done; that shame shall never depart from you. Ye should give mercy unto them that ask mercy, for a knight without mercy is without honour." Sir Gawaine was so astonished at the death of the fair lady that he knew not what he did, and he said unto the knight, "Arise, I will give thee mercy; and go thou unto King Arthur, and tell him how thou art overcome by the knight that went in the quest of the white hart." "I care not for mercy now," said the knight, "for thou hast slain my lady that I loved best of all earthly things it matters not whether I live or die." Then Sir Gawaine went into the castle and made ready to rest there all night. "What will ye do?" said Gaheris; "will ye unarm you in this country? Ye may believe ye have many enemies here." He had no sooner said that word than there came four knights well armed, and anon they made Sir Gawaine and Gaheris yield themselves as prisoners, in spite of the brave battle wherein Sir Gawaine was sore wounded in the arm. Early on the morrow there came to Sir Gawaine in the prison one of the ladies of the castle, and said, "Sir Knight, what cheer?" "Not good," said he. "It is your own fault," said the lady, "for ye have done a passing foul deed in the slaying of the lady, which will be great disgrace unto you. Be ye not of King Arthur's kin?"