Hidden Dane by Victoria Pinder

One treasure hunting professor who wants to erase his past and the one woman he can’t forget.

When Emily Mira was eighteen, Dane Pearce gave her a key as a promise of his love. Shortly after, he disappeared from her life. Now, ten years later, his troubles are following her as men with guns storm into a nightclub, looking for her.

It’s Dane’s fault men are hunting his high school sweetheart. She has something all of them want: the key to unlock a valuable, ancient treasure. After saving her from the men, he expects her to hand over the key willingly and be done with the danger. Instead, she demands to join him as his partner in search of the missing Irish Crown Jewels.

Now there’s a bounty on both of their heads. But it’s not his life or the jewels Dane is most afraid of. It’s facing the reason he left her behind in the first place.