Enigma:What Lies Beneath (Enigma Series Book 1)

Doctor Abbigail Sutherland is used to being alone. Between twelve hour shifts at the hospital and looking after her eccentric father, she has very little time for much else. Until an unexpected call one night, sends her racing to the lab where she discovers a secret that could change the world forever.
Hauke awakens after an underwater explosion, strapped to a bed and on his way to a site known as Area 51. His only hope for survival lies in Abbie Sutherland, the beautiful doctor that saved his life. Amidst a deadly virus, seemingly impossible to stop, and a corrupt Government placing a price on their heads, Hauke and Abbie run for their lives, uncovering conspiracies, deceptions, and a love that won't be denied...

Recommend reading the books in order. This is not a serial, and it does have a happy ever after, but the story moves forward with a new hero and heroine in the next book.