Harry started for the door but was blocked again, this time by Hermione.
"What is it now?" he said impatiently. He couldn't stop imagining what horrible things might be happening to his godfather at this very moment.
"Harry, you can't seriously think that thirteen students who are supposed to be under solitary confinement are just going to waltz out of Hogwarts without any trouble? We need a plan if we want to have any hope of rescuing Sirius."
Harry knew that she was right, but it was still difficult to stop himself from just flinging open the door and making a run for it. He sat down glumly at a desk. "What do you suggest?"
She flashed a brilliant smile. "I have some ideas…"
They discussed the details of the plan for several minutes, then Hermione took the invisibility cloak from Harry and put in on. Luckily, he hadn't taken it out of his bag yet when Umbridge caught them.
"Alright, so, remember, wait until I cast both spells before you take the cloak."
They heard her mutter the disillusionment charm first. It would hide the open door from sight while they escaped. A moment later they heard her say the shrinking spell, which was the signal for them to pull the cloak back into the room.
Luna was next. She donned the invisibility cloak and stepped just outside the door. They heard her mutter diminuendo, then heard the soft rustle of the cloak as it fell to the floor. As Harry bent down and retrieved the cloak again, he could see a very tiny Luna making her way to the baseboards against the wall. Harry was the last one out, and he closed the door behind him. He cast the counterspell for the disillusionmentcharm, then gathered up the others and started towards the front gate.
He went as quickly as he could, but his progress was slowed when supper ended, and hordes of students flooded out of the Great Hall. He walked pressed up against the wall, careful to avoid bumping into anyone.
He kept going until he spotted Draco Malfoy. The sight of the slicked-back blonde hair of their betrayer filled him with rage that he was in no mood to suppress. He squeezed his way through the crowd, then stuck his foot in front of Malfoy and watched with satisfaction as he tumbled headlong onto the floor.
Crabbe and Goyle, his two cronies, clumsily helped him to his feet. "Are you ok, Draco?" they simpered.
"I'm fine," he said, brushing them off.
"What happened?" Crabbe said.
Goyle elbowed him roughly. "He tripped, obviously."
"I didn't trip," Malfoy said, looking around angrily. "Someone tripped me. I felt it."
"But who?" Crabbe asked. He turned to Goyle. "I didn't see anyone, did you?"
The other oafish boy shrugged his shoulders. "Don't think so."
Harry watched as Malfoy's eyes narrowed dangerously. He stared hard at the space in front of him, right where Harry was standing. He reached out his hand slowly, growing closer and closer until his fingertips were no more than a hairbreadth away from touching the cloak. Harry snapped back to his senses and drew away just in time.
"What'cha doing, Draco?" Goyle asked, watching him in confusion.
"Nothing," he muttered darkly. "Let's go." He retracted his hand and stalked away, Crabbe and Goyle following close behind.
Harry could hear his friends quietly cheering him as he continued down the hallway. They made it to the main entrance without any more trouble, then headed straight for the training grounds. To his relief, the brooms from the last flying class of the day hadn't been put away yet. Mrs. Hooch was nowhere to be seen either. He had never been gladder that their flying teacher wasn't the responsible sort.
He shed the invisibility cloak and quickly reverted the others to their normal size.
"Alright guys," he said as he picked up a broom, "let's do this."
Harry spent the entire trip to London willing his broom with every ounce of his strength to go faster. Hold on, Sirius, he pleaded over and over in his head. Please hold on.