First to Burn (Immortal Vikings, 1)

A soldier with secrets Immortal Viking Wulf Wardsen once battled alongside Beowulf, and now serves in Afghanistan. He's trusted the mortal men on his elite special operations team to protect his secret, until an explosion lands Wulf in a place more dangerous to him than a battlefield: a medevac helicopter. 

A doctor with questions Army captain Theresa Chiesa follows the rules and expects the same from others, even special forces hotshots like Sergeant Wardsen. She's determined to discover the secret behind his supernaturally fast healing, and she won't allow his sexy smile to distract her. 

An enemy with nothing to lose Even as Theresa's investigation threatens to expose him, Wulf is stirred by her passion. Dreaming of love and a normal life, he wants nothing more than to build a future with her. But the lost Viking relic needed to reverse his immortality is being hunted by another—an ancient enemy who won't hesitate to hurt Theresa to strike back at Wulf. 

Book one of the Immortal Vikings series.