Crookshanks darted up first; he had evidently pressed his paw to the knot on the trunk, because Lupin, Pettigrew, and Ron clambered upward without any sound of savaging branches.

 Black saw Snape up through the hole, then stood back for Harry and Hermione to pass. At last, all of them were out. 

The grounds were very dark now; the only light came from the distant windows of the castle. Without a word, they set off. Pettigrew was still wheezing and occasionally whimpering. Harry's mind was buzzing. He was going to leave the Dursleys. He was going to live with Sirius Black, his parents' best friend.... He felt dazed.... What would happen when he told the Dursleys he was going to live with the convict they'd seen on television... !

 "One wrong move, Peter," said Lupin threateningly ahead. His wand was still pointed sideways at Pettigrew's chest. 

Harry heard Amelia hiss in a cat-like manner; he was sure he could see claws where her nails should be.

Silently they tramped through the grounds, the castle lights growing slowly larger. Snape was still drifting weirdly ahead of Black, his chin bumping on his chest. And then - 

A cloud shifted. There were suddenly dim shadows on the ground. Their party was bathed in moonlight. 

Snape collided with Lupin, Pettigrew, and Ron, who had stopped abruptly. Black froze. He flung out one arm to make Harry, Hermione, and Amelia stop.

Amelia cursed. 

Harry could see Lupin's silhouette. He had gone rigid. Then his limbs began to shake. 

"Oh, my --" Hermione gasped. "He didn't take his potion tonight! He's not safe!"

 "Run," Black whispered.  "Run. Now."

 But Harry couldn't run. Ron was chained to Pettigrew and Lupin. He leapt forward but Black caught him around the chest and threw him back. 

"Leave it to me -- RUN!"