In plain words
Then Rāma told Lakṣmaṇa to keep watch over Sītā and not to leave her alone whatever the circumstances, and he himself went chasing that deer of illusion. However far he went, the deer would not be caught, so he loosed a missile. The moment it struck, Mārīca took his own true form and, mimicking Rāma's voice: “Ah, Sītā! Ah, Lakṣmaṇa!” he cried out, and fell to the ground. Hearing it, Sītā grew alarmed: “Lakṣmaṇa! Your brother seems to be caught in some danger and calling you. Go to his help at once,” she said, and hurried him in many ways. Then Lakṣmaṇa: “Mother! No demon whatever can do anything to Rāmacandra. Don't be alarmed; be brave,” he said. But in however many ways Lakṣmaṇa spoke words of courage, Sītā would not listen. Worse still: “With Rāma gone, are you looking to keep me for yourself?” she said, words that ought not to be spoken. Lakṣmaṇa's mind was deeply pained. ‘Has Sītā, who is like a mother, spoken such words to me?!’ So, with a shaken mind, he set out from there. Before going, he drew a line around the leaf hut: “Mother! Whatever the circumstances, you must not cross this line and go outside,” he said. She agreed. After Lakṣmaṇa had gone from there, Rāvaṇa came dressed as a sage: “Mother! Hungry, hungry!” he said. As soon as she heard the word ‘hungry’, Sītā felt pity for him. Thinking it a woman's Dharma to give food to one who is hungry, she said, “Come in, my son!” But he was afraid to cross that line. However long it went on, he would not cross the line and come in, but kept on crying, ‘Hungry, hungry!’ Then, having no choice, she herself crossed the line and came out. At once Rāvaṇa carried her off in his chariot. Rāma and Lakṣmaṇa came back to the leaf hut, and by then Sītā was not there. Rāma, voicing his grief: “Lakṣmaṇa! Why did you leave Sītā alone and come?” he asked. Lakṣmaṇa: “Brother! Sister-in-law said words to me that ought not to be spoken or heard. I left her and came only because I could not bear to hear those words. Otherwise I would not have left her,” he said. Sītā too, sitting in the Aśoka grove, went on grieving deeply for the words she ought not to have spoken to Lakṣmaṇa: