"Turn out your pockets, or we go straight to the headmaster! Pull them out, Potter!" 

Cold with dread, Harry slowly pulled out the bag of Zonko's tricks and the Marauder's Map. 

Snape picked up the Zonko's bag. 

"Ron gave them to me," said Harry, praying he'd get a chance to tip Ron off before Snape saw him. "He -brought them back from Hogsmeade last time --" 

"Indeed? And you've been carrying them around ever since? How very touching... and what is this?" 

Snape had picked up the map. Harry tried with all his might to keep his face impassive.

 "Spare bit of parchment," he said with a shrug.

 Snape turned it over, his eyes on Harry. 

"Surely you don't need such a very old piece of parchment?" he said. "Why don't I just -- throw this away?" 

His hand moved toward the fire. 

"No!" Harry said quickly. 

"So!" said Snape, his long nostrils quivering. "Is this another treasured gift from Mr. Weasley? Or is it -- something else? A letter, perhaps, written in invisible ink? Or -- instructions to get into Hogsmeade without passing the dementors?"

 Harry blinked. Snape's eyes gleamed. 

"Let me see, let me see...." he muttered, taking out his wand and smoothing the map out on his desk. "Reveal your secret!" he said, touching the wand to the parchment.