The Bear's Healing Touch. Tales of the Were - Grizzly Cove, #7

Sven had given up on love, but in the midst of crisis, it showed up at his door. Sirena has been gravely injured by an evil sea monster and put into the care of Grizzly Cove's only doctor. Sven is a retired soldier, like most of the other guys in Grizzly Cove, but he'd dedicated his life to medicine and helping the new town get on its feet. He doesn't think he'll ever find a mate, but he's content to let the others settle down and find happiness, while he tends to them all.
Until they send a gravely injured mermaid his way. Sirena gets under his skin. She brings out all sorts of protective instincts and desires. She infuriates him and beguiles him in equal measure, but most of all, she worries him. She's not getting any better, despite his best efforts. He calls in magical reinforcements and the best experts he can find to try to help her, but the evil creature still has its hooks in her and it won't let go without a fight.