be under the spell of (someone)

To be influenced or controlled by someone because one finds them fascinating, enchanting, or seductive. Our son has never acted out like this before. I think he must be under the spell of that new friend of his. Such was the magnitude of her beauty that countless men have been under the spell of the duchess. I would normally never rush into a relationship this quickly, but I was under the spell of that mysterious woman and found her completely captivating.