After considering several possibilities from the flight arriving at the specified time, Perrache selects François Perrin, an unsuspecting violinist, who is noticeable because, as the result of a practical joke played on him by his fellow orchestra members, he has arrived wearing a black shoe on one foot and a reddish-brown one on the other. Milan takes the bait and immediately begins a series of attempts to discover what Perrin knows—never realizing the fact that Perrin knows nothing at all about espionage (although he is an expert on music). Milan's machinations place Perrin in a series of increasingly peculiar adventures which he either avoids or escapes from by pure luck (which only confirm Milan's increasingly paranoid suspicions), and although Perrin is largely oblivious to the mayhem occurring around him, he cannot help noticing Milan's top agent, the beautiful "femme fatale" Christine. Adding to the confusion is the fact that Perrin is having an affair with Paulette Lefebvre, the wife of his best friend Maurice (both of whom are musicians in the same orchestra as Perrin), and Maurice, upon accidentally hearing a recording of Perrin and Paulette having torrid sex (made by Milan's agents and listened to inside a floral delivery truck), jumps to the mistaken conclusion that Paulette is having an affair with a florist. All the time, Toulouse and Perrache watch the chaos serenely, although Perrache is troubled by his chief's callousness toward the risk that Perrin might be killed.