In 1935, United States Narcotics Agent Michael Barrows (Powell) is assigned to find an unidentified freighter suspected of smuggling drugs.

The trail leads him to Shanghai, where his Chinese counterpart, Commissioner Lum Chi Chow (Vladimir Sokoloff), has obtained information from a dying man.

During his investigation, Barrows meets recent widow Ann Grant (Signe Hasso), who is preparing to send orphan Chinese teenager Shu Pan Wu (Maylia) to the safety of the United States.

An alert agent spots them being transferred to innocent-looking butter containers sent aboard a ship bound for New York via Havana under the watchful eye of Naftalie Vrandstadter (an uncredited Ivan Triesault).

When first released Thomas M. Pyror of The New York Times gave the film a mixed review, and wrote, "To the Ends of the Earth, for all the journalistic austerity of its introductory sequences inside the narcotics division of the Treasury Department and at the United Nations council table in Lake Success, is predominantly a cops-and-robbers tale that relies too heavily on physical violence to make its impress.

Unfortunately, this heightens the synthetic flavor of the picture and accounts in large measure for the attitudinized nature of the story's development that lessens its over-all dramatic impact...The author of all this, Mr. Kennedy, has concocted a highly involved and complicated screen play that sparkles and sputters as far as dramatic effectiveness goes, and thereby imposes an average look upon a picture which, with a little more resourcefulness, might easily have been distinctive.

"[3] The staff at TV Guide liked the film and wrote, "An engrossing, globetrotting semi-documentary on the evils of narcotics pushers, specifically those who try smuggling opium onto U.S.