He might not have known, but Zacharias did. And he let the kiss deepen naturally. The tip of his tongue traced along the rim of Merlin's lips, and urged them apart, taking his time to do so, so that he could lick into his mouth, just light and testing.
And yet Merlin was trembling, shaking like a leaf in his arms, and he couldn't help but notice that. When he broken the kiss, his eyes opened and he frowned a little bit.
"Do I scare you that much?" he asked him. He knew he put Merlin on edge, but he hadn't been out to frighten him.