Maestro Barenboim is clearing out his attic to make room for his soon-to-be musical guests arriving for the International Classical Music Week. When Max, Emilia, Leon and Maurice find a golden, ornate jewelled egg in the park, they set off in search of the owner, true to their cinematic role models, the space detectives. But the investigation remains fruitless for the time being. Only when the four spot Pascal in the park with his dog and a suspicious-looking suitcase, and Leon gets the idea to reconstruct what happened on the basis of the footprints left in the sand at the scene of the crime, do the young detectives make progress.