So when he was departed King Mark bethought him of more treason: notwithstanding King Mark granted Sir Percivale never by no manner of means to hurt Sir Tristram.

So anon King Mark sent unto Sir Dinas the Seneschal that he should put down all the people that he had raised, for he sent him an oath that he would go himself unto the Pope of Rome to war upon the miscreants; and this is a fairer war than thus to arise the people against your king.

When Sir Dinas understood that King Mark would go upon the miscreants, then Sir Dinas in all the haste put down all the people; and when the people were departed every man to his home, then King Mark espied where was Sir Tristram with La Beale Isoud; and there by treason King Mark let take him and put him in prison, contrary to his promise that he made unto Sir Percivale.
When Queen Isoud understood that Sir Tristram was in prison she made as great sorrow as ever made lady or gentlewoman.

Then Sir Tristram sent a letter unto La Beale Isoud, and prayed her to be his good lady; and if it pleased her to make a vessel ready for her and him, he would go with her unto the realm of Logris, that is this land.

When La Beale Isoud understood Sir Tristram's letters and his intent, she sent him another, and bade him be of good comfort, for she would do make the vessel ready, and all thing to purpose.
Then La Beale Isoud sent unto Sir Dinas, and to Sadok, and prayed them in anywise to take King Mark, and put him in prison, unto the time that she and Sir Tristram were departed unto the realm of Logris.