The night before the derby

The night before the derby, the referee's whistle vanished from its usual place. Nobody asked for it, nobody saw it leave and everybody has a theory. Four people and one whistle: 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

• Albano, the referee: He's refereed matches for twenty years. He says he's never seen anything odd, but he's never taken his sunglasses off either.
• Belmira, the referee assessor: She marks referees in a notebook. Nobody knows what criteria she uses, not even her.
• Custódio, the kit man: He washes both teams' kit and hears the conversations in both changing rooms.
• Deolinda, the cleaner: She cleans the stadium after every match. She finds everything in the stands, even promises.