Found: Historical romance Knights Templar treasure

The heroine of the book is a widow who was married off when she was young to a much older man. The heroine later tells the hero that the one time she tried to initiate 'relations' with her husband, he was appalled and told her to never do so again, hence her being a virgin despite years of marriage. At the end of the book, the heroine and the 'hero' realize her first husband was actually a Templar Knight, who kept his vows despite living in secret to avoid execution. And the first husband was guarding Templar treasure.

All I can remember about the hero is that he didn't tell the heroine that he was there investigating things/treasure hunting.

I think the setting was in a medieval aged castle, approximately 1350 AD or so. Perhaps in Scotland? And I do believe they found some sort of treasure at the end of the book, but I'm not certain.

I borrowed this book from the library approximately 10 years ago, so I don't know it's exact age. It was a paperback book.

Now I'm second guessing when I read it. I'll leave it in the post, but it's possible I read less than 10 years ago.

Lord of a Thousand Nights by Madeline Hunter?

This is it!!! Thank you so much, it's been driving me insane!

You're welcome.