The Hermit Kingdom

Shane Riley, ex-Australian Special Forces, is a retrieval specialist.

People want something, and he finds it, no matter where it is. He works for rich power brokers, collectors, black market dealers, and anyone willing to pay the right price.
He only has one rule: he does not retrieve people.
He gets interrupted on an offshore dive, and the two men requesting his presence bring him to a rich politician in South Korea, who wants his help.
His daughter's been taken by a government entity in North Korea, and he wants Shane to get her back.
Shane balks, citing his "one rule," but this time the South Korean man knows exactly what will entice him to help. His daughter, he claims, was trying to contact Shane's wife before she was taken.
...Shane's wife - who was murdered a year ago.