What circumstances first bring Heathcliff to the Heights in the book Wuthering Heights?

Mr Earnshaw brings him back from Liverpool, if I remember rightly. He finds him as an orphan - he doesn't speak any English and he has no family or anything like that.

In Victorian England the impropriety of adopting such a "gypsy orphan" and raising as your own points to the unlikelihood of the brief explanation that Mr Earshaw provides about the origins of Heathcliff.

If you think the narrator is incompetent for leaving this issue unexamined, you will find many clues to the problem of Heathcliff's origin in the early chapters. Heathcliff's origin is the "key" to the entire novel.