Cleaning at seven

The cleaning team comes in at seven and knows every drawer in Parliament better than the MPs. That morning, the first thing they found was an open drawer. Four people and one piece of evidence: 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

• Arlete, the cleaning supervisor: She shares out the rooms among her colleagues. The leader's always goes to her.
• Belarmino, the plumber: He came to fix a tap that's been dripping for two years. He picked that day.
• Carminda, the lady with the trolley: She pushes the cleaning trolley along the corridors. A lot fits inside that trolley.
• Diamantino, the IT technician: He came to look at a computer that won't switch on. He switched it on and off three times.