I’ve dreamt in my life dreams that have stayed with me ever after, and changed my ideas: they’ve gone through and through me, like wine through water, and altered the colour of my mind.

Catherine says this to Nelly just before she tells the dream of being sent from heaven back to earth, where she wept so hard that the angels threw her out onto the heath. It is the chapter in which she explains her choice between Edgar and Heathcliff.