New York, 1959: It's the afternoon of a major charity event, and in a New York hotel, two absolute giants of music history meet for a crucial rehearsal. Ruthlessly thrown onto the stage together by their agents, the situation between the two stars couldn't be more explosive: While the easygoing crooner Dean Martin secretly adores the legendary "Little Sparrow of Paris," Edith Piaf initially feels only pure hatred for the American entertainer in his tailored suit.

What the proud chansonnière doesn't realize, however, is that her shining star in America is threatening to fade. After scandalous drug escapades and concerts canceled at short notice due to illness and exhaustion, she has fallen out of favor with US audiences. The "Italian crooner" Dean Martin was hired behind her back for one purpose only: to boost sluggish ticket sales with his massive star power.

And so the comical, highly efficient battle between two show business giants for the evening's performance program begins its unstoppable course. Between immortal melodies and biting verbal sparring, the entire lives and work of both icons are suddenly put to the test. But the fiercer the singing war rages, the more the painstakingly maintained facades crumble. When they have finally torn away all the masks of show business from each other, the hostility gives way to an unexpected closeness – intimate confessions follow, and the two even begin to genuinely like each other.