The evil knight Torchesac, who is at the service of the sinister lord of La Mortaille, gets a very powerful magic flute and uses it for evil purposes. Johan and Pirlouit, assisted by the magician Homnibus, travel to the land of the Smurfs, the only manufacturers of this sort of instrument, to get a new one and battle the usurpers.

Ex-agent of the Secret Service and colonel to Her Most Gracious Majesty, Sir Harold Wilberforce Clifton has become an amateur detective.