Anybody recognize this book?

[honorharrington]

I'm looking for a book that I read years and years ago. It would have been published in the 60s or 70s...possibly the very early 80s. It was about a fairly newly wed wife whose husband is spending most of his time locked away in...a lab or a basement work place maybe? Anyway, this woman comes to realize that they are reincarnated souls doomed to never find love because in their first encounter centuries before he was cursed by her. I think she was killed, possibly for being accused a witch, but anyway, one of them died before she could forgive him for his betrayal of her. So they went through at least two more lives, coming across each other but with heartbreak until this woman finally figures out what's happened and she forgives him.

It's not Green Darkness by Anya Seton. I have that one. And it's not Lady of Hay by Barbara Erskine, although I've read that one since.

Any other ideas of what it might be? This has been driving me nuts for years!