‘The key’s in the lock,’ Harry muttered. ‘We could lock it in.’ ‘Good idea,’ said Ron nervously. They edged towards the open door, mouths dry, praying the troll wasn’t about to come out of it. With one great leap, Harry managed to grab the key, slam the door and lock it. ‘Yes!’ Flushed with their victory they started to run back up the passage, but as they reached the corner they heard something that made their hearts stop ...