‘The number of times I saw James disappearing under it …’ said Lupin, waving an impatient hand again. ‘The point is, even if you’re wearing an Invisibility Cloak you show up on the Marauder’s Map. I watched you cross the grounds and enter Hagrid’s hut. Twenty minutes later, you left Hagrid, and set off back towards the castle. But you were now accompanied by somebody else.’ ‘What?’ said Harry. ‘No, we weren’t!’ ‘I couldn’t believe my eyes,’ said Lupin, still pacing, and ignoring Harry’s interruption. ‘I thought the map must be malfunctioning. How could he be with you?’
