She asks her maid Gisèle to prepare her gala outfit for that day and to take care of the little diamond heart that she would like to wear on this occasion (a trifle of 500,000 new francs, or some 760,000 euros).
Richard, a nice tiler working in the star's house, exasperated by Corinne, his ambitious and troublesome girlfriend, incidentally learned of the existence of the famous jewel from Gisèle... At nightfall, he steals the little heart, but neighbors, having seen him crossing the wall of Mylène's property, alert the police.
Pursued by the police, Richard takes refuge in the nearest warehouse, that of a music store, and hides the jewel by sticking it with chewing gum inside an Ericson electric guitar.
The next day, when tough Corinne goes to the store to buy the guitar, the five Ericson copies in stock have just been sold to five singing idols.
They will have to approach the idols during their artistic performances to find the one among the five who holds the famous treasure guitar: is it Charles Aznavour, Sylvie Vartan, Frank Alamo, Nancy Holloway or Johnny Hallyday?