It turns out that the Hogwarts in J.K. Rowling's book is not exactly the same as the one in the films and games. This one is built backwards and inside out, and the stairs move around in more than one direction. Also, the suits of armour keep walking around, the people in the portraits won't stay still... it's all very confusing.
You realise you need your map after all, and turn to go back to the Gryffindor common room - before you realise you have no idea where it is. You are well and truly lost.
You wail in frustration and stomp down a flight of stairs. Your foot becomes lodged in the false step halfway down. You stop and try to think what flight of stairs had the false step in the books. What floor was this?
You hear footsteps behind you, and it turns out to be Percy. You recognise his ginger hair and superior countenance. He's also wearing a gleaming prefect badge, which you suspect he's been up all night, cleaning.
'What are you doing here?' he asks, and hauls you out of the gap in the stairs. He glances at the scar.
'You must be Harry Potter,' he remarked. 'What lesson do you have now?'
Percy leads you to Professor McGonagall's classroom, and she gestures at you to have a seat. You see her nostrils flare in annoyance.
You take a seat next to...