Shattered: The Final Act. - The Shattered Series Book 4, #4

Leaving a lover and trouble behind in Paris, Jo has settled into an easy life in New Zealand with a different name. She's even learning to make pottery. One morning, while returning a book to the library where a new friend works, she discovers the librarian is trying to hide her tears. When pressed for details, Jo discovers the woman's sister is missing. Along with her boyfriend, who, like Jo is a Canadian.
Jo does her best to not get involved but relents with a promise to help locate the missing girl and that's all. The trail will lead Jo to one of Diamond Harbour's richest inhabitants, regardless of being warned away. She hears rumours of stolen cash, trading in body parts and ruthless gangsters. She's in too deep to turn her head. The young man, the boyfriend, is being kept alive because a rich man's daughter is on her deathbed and needs his kidneys.
Both of them. Jo won't be alone. There's a vigilante looking for the teenager too.