Whilst Launcelot was sleeping Sir Turquine appeared and carried Lionel off and threw him naked in his dungeon with rest of his collection of naked knights. Launcelot's brother Sir Ector de Maris tracked Lionel down but ended up the same way.
Fortunately he was rescued by the daughter of King Bagdemagus who took him out through the twelve locks in return for promising to fight for her dad against the King of Northgalis at the next tourney. On his way he crashed in a handy pavillion but whilst sleeping was mistaken by Lord Belleus for his lady and snogged. After that was cleared up and Belleus' wounds staunched he carried on to meet Bagdemagus and his daughter at their abbey, and promised to fight on Tuesday.
After a thank-you party he then set off in search of Lionel.
After a long bloody dual with conversation (during which he discovered he had already killed Turquine's brother) Launcelot triumphed, and sent the eternally grateful Gaheris to free Ector, Lionel and the other captive knights while he kept his promise to the damosel.
Then he killed two evil giants that had imprisoned sixty women in Tintagil Castle for seven years.
One night he heard a commotion outside his remote lodging, and investigating he rescued Sir Kay from three other knights, then the next morning he quietly snuck off in Kay's kit.
After successfully intimidating his way into the chapel past thirty black knights he found a bloody cloth wrapped around the cooling remains of Sir Gilbert, and braving earth-tremors he grabbed a likely-looking sword too.
Upon exit he was accosted by Hellawes herself, who made the astonishing admission that she had already had Gawaine (who had hacked off Gilbert's left hand in an earlier fracas), but really fancied Launcelot so much she wanted him mounted (in the taxidermalogical sense). When he kept it in his pants she died of frustration a fortnight later, and Launcelot returned with the damosel to heal Sir Meliot, before returning to his wanderings.
Then he failed to stop Sir Pedivere beheading his own wife on suspicion of shagging her cousin before returning home to boast modestly.