Adult Romance book - Killers meet each other and there’s a mission where they kill a bunch of people to steal something and save the world

[Agatha]

Basically a mr and mrs smith book?

[Kris]

Agatha, I moved your request to the "Unsolved" folder because you're looking for one specific book.

Who do the hero and heroine work for?
What is the story's location and time period?

Around what year did you read this book?