The air is still, but a storm is brewing. Merlin and Vivien are resting beneath an oak tree in the forest of Broceliande.
Much earlier, Arthur's enemy, Mark of Cornwall, had heard the rumor in Camelot that Lancelot and the queen were carrying on an adulterous affair in secret. He was also told that the influence of this corruption was slowly spreading among others at the court. Mark decided to send Vivien, his paramour, to Camelot in order that she might take advantage of this delicate situation and stir up additional trouble.
Upon her arrival at court, Vivien had appealed to Guinevere for sanctuary and claimed to be an innocent orphan maiden who had just escaped from the torments of Mark. Her request was granted and Vivien was made one of the ladies in waiting. Having attained this position, Vivien spent her time ferreting out information, spreading scandalous stories, and causing other kinds of unrest. As part of her plan, she attempted to gain the confidence of Arthur, but the king wanted nothing to do with her. The story of Vivien's failure spread through the court and made her a subject of laughter for a while. This mocking infuriated her and made her more determined in her evil intentions.
One of the most famous and important men in Camelot was Merlin, the great magician, astronomer, engineer, architect, and bard, whose friendship and wise advice were valuable assets to Arthur. Vivien made a concerted effort to gain the old man's favor. She eventually succeeded, for though he did not like her, he was amused by her feline mannerisms and complimented by her attentions. Vivien even claimed to be in love with him. Merlin was too wise to believe her, but he was old and lonely and sometimes his certainty would weaken.
A time came when Merlin fell into a state of deep depression. He wandered alone on the beach and then drifted off in a small boat that he found, but Vivien followed and joined him. At first he was unaware of her presence; then he pretended to ignore her. Finally they came ashore in Brittany and continued to wander until they reached the forest of Broceliande. Vivien had gone to all this effort because she recalled that Merlin had once mentioned a potent magic charm he knew. Through this spell a man could be made as if imprisoned in an impregnable tower and would be invisible to all the world except the one who worked the charm. Vivien now sought to learn this secret and use it on Merlin, which is how the two came to be resting together in the forest.
As they recline beneath the tree, Vivien caresses and kisses Merlin's feet and beard and chatters to him of her love and devotion. Merlin is delighted by her talk, but does not believe even a part of it. Nonetheless, since he owes her a boon, he promises to grant her wish. Vivien asks to be taught the secret charm as an expression of his trust in her and proof that he returns her love, but Merlin refuses. In addition, he berates himself for ever having revealed the existence of the secret to her. He justifies his refusal by his fears that she would misuse the charm and offers her anything else she desires.
Vivien now begins to make use of all her varied feminine wiles in order to lure Merlin into her trap; she is coy, she weeps, she sings:
"In love, if love be love, if love be ours,
Faith and unfaith can ne'er be equal powers:
Unfaith in aught is want of faith in all."
For an instant, Merlin nearly believes her to be truly in love with him, but he manages to regain his senses.
He attempts to distract Vivien by telling her anecdotes about his youth, but she always manages to guide the conversation back to the same subject — whether or not he responds equally to her love for him, and whether he will continue to "mistreat" her and "exploit" her devotion. Merlin continues to deny her request. Now Vivien pretends to be indignant, as if he had insulted her. Finally Merlin tells her the ancient legend attached to the origin of the charm, hoping to satisfy her that way. But this indication of lessening resistance encourages Vivien. She maintains her assault on him, using every wile to seduce him to her wishes.
As their conversation continues, it is evident that Merlin really understands what a vicious and evil person Vivien is, but he is old and tired and cannot help but find her pretended affection for him complimentary. In one last effort, he orders her to leave him and calls her a harlot. Vivien is angered, but she hides her rage and behaves as if she were a wronged and misused maiden. She swears she is innocent of evil intentions and refuses to respond to any more of his advances. Finally, in terror of the impending storm, she throws herself upon Merlin for protection. His resistance is now at its lowest ebb; he takes pity on her, teaches her the charm, and falls into an exhausted sleep.
Then, in one moment, she put forth the charm
Of woven paces and of waving hands,
And in the hollow oak he lay as dead,
And lost to life and use and name and fame.
Then crying, "I have made his glory mine,"
And shrieking out, "O fool!" the harlot leapt
Adown the forest, and the thicket closed
Behind her, and the forest echo'd "fool."