The sound desk

In the control room there were three mixing desks, dozens of buttons and one person staring at a phone. That was where the anthem's sound went out to the broadcast. The earpiece passed through there too, and never came back. Four people and an earpiece: one person per row, one per column. Whoever is left alone with it in the same room is the one you're looking for.

Suspects

• Armindo, the camera operator: He filmed the anthem up close. He says it all looked fine; what couldn't be heard wasn't his department.
• Brígida, the sound mixer: She has three mixing desks and two hands. She says she did what she could with the maths she had.
• Casimiro, the track electrician: He answers for every cable on the site. Some of the cables lead to things he's never seen.
• Dulcineia, the broadcast intern: She was staring at her phone. She says it was work: she was checking how the broadcast was coming out.