His horse was taken from him by enchantment, so Lancelot, in order sooner to overtake the queen, rode on in a cart.

This was considered a disgraceful mode of progress for a knight, as a nobleman in those days was condemned to ride in a cart in punishment for crimes for which common people were sentenced to the pillory.
Lancelot succeeded in reaching the castle of Guinevere's kidnaper, whom he challenged and defeated.

The queen, instead of showing herself grateful for this devotion, soon became needlessly jealous, and in a fit of anger taunted her lover about his journey in the cart.

This remark sufficed to unsettle the hero's evidently very tottering reason, and he roamed wildly about until the queen recognized her error, and sent twenty-three knights in search of him.

They journeyed far and wide for two whole years without finding him.
"'Then Sir Bors had ridden on Softly, and sorrowing for our Lancelot, Because his former madness, once the talk And scandal of our table, had return'd; For Lancelot's kith and kin so worship him That ill to him is ill to them.'" TENNYSON, _The Holy Grail_.
Finally a fair and pious damsel took pity upon the frenzied knight, and seeing that he had atoned by suffering for all his sins, she had him borne into the chamber where the Holy Grail was kept; "and then there came a holy man, who uncovered the vessel, and so by miracle, and by virtue of that holy vessel, Sir Lancelot was all healed and recovered." [Sidenote: Gareth and Lynette.] Sane once more, Lancelot now returned to Camelot, where the king, queen, and all the knights of the Round Table rejoiced to see him.