Hardy Boys: The Arctic Patrol Mystery by Franklin W. Dixon (Vintage 1969 Edition)

Private investigator Fenton Hardy enlists the aid of his teenage detective sons in a search for a missing man being sought by an insurance company. All leads to the sailor’s whereabouts have petered out and the boys fly to Iceland, the man’s native land, hoping to find a new clue. From the moment Frank and Joe arrive in Reykjavik, the capital city of Iceland, they are in constant danger.  In the spine-chilling pursuit that follows, Frank and Joe uncover a diabolical espionage plot that threatens the life of a U.S. astronaut and NASA’S moon project.