Bing Crosby is an insurance investigator sent to Ireland to look for the stolen Blarney Stone. There he finds Barry Fitzgerald (in his fourth and final pairing with Der Bingle), the local sergeant of the Garda. Ann Blyth is Fitzgerald's daughter. Between the usual courting, misunderstanding and songs, as well as an old prediction puzzled out by Eileen Crowe, it takes half the movie before the investigation gets underway.
There are a couple of new songs, including the title song. That's sung three or four times. Older and traditional songs make up the balance. They serve to punctuate the scenes, rather than advance the plot or express the emotions of the moment, as they do in better musicals. Miss Blyth only gets one duet with Crosby. Despite her ability, it wouldn't be until she got to MGM that she got a chance to show off her voice.
DP Lionel Lindon, unusually for American cinematographers, lights the scenes rather than the actors and seems surer with interior sets rather than outdoors. His unflattering non-portraiture makes it appear like steel engravings and makes me think this would have been better shot in color. Lindon's facility for scenery meant he spent his later career doing science fiction movies, AROUND THE WORLD IN EIGHTY DAYS (for which he won an Oscar) and the 3D JIVARO.