"Slow down," said Professor McGonagall, "and start from the beginning."

Leo sighed. His attempts to explain exactly what was going on had not been going well; in fact, Professor McGonagall had dismissed him out of hand until Professor Dumbledore suddenly returned. The Headmaster had a lot more interest in hearing what he had to say, but Leo was too panicked by this stage to express himself clearly.

"The Heir of Slytherin chose to take Ginny down into the Chamber as a trap for Potter," said Leo patiently. "We need to stop Potter from walking into this trap."

"Potter does not know where the Chamber of Secrets is!" said Professor McGonagall hotly.

"The Heir thinks he does, the Heir thinks Potter has enough information to work it out!"

"Then surely, since you have the same information as Potter, you should also be able to work it out?"

This was a direct challenge, and Leo wasn't going to turn it down… but he had no idea. Think, he told himself. There had to be some location… some significant event… "There was a girl who died last time the Chamber was opened," he said. "Where did she die?"

"In the girls' bathroom on the second floor," answered Professor Dumbledore.

Something about that rang a bell. Girls' bathroom… dead body… it was near there that the cat had been attacked… a ghost! Yes! "The girls' bathroom is haunted!" said Leo triumphantly. "Could it be that girl? Could the entrance to the Chamber be in that bathroom?"

"It's certainly possible…" said Professor Dumbledore cautiously.

"It's just the sort of conclusion Potter would jump to as well," said Professor McGonagall.

By unspoken agreement, the three of them jumped to their feet and set off at a run towards Gryffindor Tower.

Leo would have been hopelessly lost in seconds, having never needed to go to the Gryffindor common room, but fortunately both teachers knew the way very well indeed and it only took them minutes to reach it from the staff room.

He ignored the extremely hostile stares he was being given from the Gryffindors and looked frantically around for Potter. There was no sign of him.

"Has anyone seen Harry Potter?" asked Professor McGonagall.

There were a few non-committal murmurs.

"When was he last seen?" asked Professor Dumbledore, but Leo had no patience for this sorting out of rumours, he knew where Potter would be and he had to get there before it was too late. He turned and ran pell-mell down the stairs towards the second-floor bathroom.

He tore down the stairs that led somewhere different on Tuesdays without even stopping to think what day of the week it was (thankfully, it was Monday), he ran down the formerly-forbidden third-floor corridor, nearly fell down the central staircase, and finally came to a halt, gasping for breath and nursing a stitch in his side, outside the bathroom.

Leo took a single deep breath and then flung open the door. The room was empty, except for a large black hole under the sink and a mournful-looking ghost.

"Myrtle," he said, praying he'd remembered her name right from what Marisa had told him, "I need to ask you something important."

The ghost nodded, as much as a ghost could be said to nod.

"Have you seen Harry Potter go," he gestured to the hole, "in there?"

"Yes," said the ghost. "He was with his friend Ronald and Professor Lockhart. If you're going down after him, tell him that if he dies, he's welcome to share my toilet."

Leo blinked. Professor Lockhart? If it had been anyone else he would have been relieved that there was a responsible adult down there, but the Defence Professor, of all people…

"Thanks," he said to Myrtle, "I will."

He knew that the sensible, responsible thing to do would be to tell Dumbledore and McGonagall immediately that it was too late. But Leo was done being sensible and responsible. He knew that it was time to take some decisive action.

So, he slipped his legs into the chute leading down to the Chamber and pushed himself down before he could change his mind.