Thriller w/ romantic subplot recs?

Ive been really enjoying thrillers with a touch of romance in them. I recently read the Ffion Morgan series by Clare Mackintosh (waiting on the third book) and I really liked the slow burn romance along with the thrilling mystery. Recursion by Blake Crouch too, loved the mix of a fast paced thriller w a touch of romance in the end. And I also read The Housemaid series which I enjoyed.

I’m looking for a standalone book. If I read a book from a series, I’m going to want to finish the whole series lol. Please lmk any good recs!!