Severus Snape was avoiding him. There was no other explanation.

Harry had answered every question correctly in Potions.  Snape had stopped calling on him.

He'd brewed his potions perfectly.  Snape had made his scrutiny of Harry's potions as brief and perfunctory as possible.

He'd gone to Snape's office to go over his final paper for the term.  Snape had abruptly canceled his office hours for the day.

That was why Harry had to try climbing the Whomping Willow again.

Well, that and Malfoy.  It was Malfoy who had sent his Potions textbook flying deep into the tree.  He'd meant to destroy it, but it had fallen between two large limbs instead.  Folded between the pages of that text were handwritten notes on several potions from his world.  Potions that would greatly interest someone like Snape.  Since none of Harry's notes had been transported with him, he'd spent the last few nights wracking his brains for every detail.  He was sure if he presented the material, Snape would be too curious to turn him away. 

Harry had thrown a stone at the knot that stilled the Whomping Willow.  He'd made it halfway up the trunk when a hex from Malfoy threw him back on the ground.  It wasn't until Hermione arrived and held off Malfoy and his goons that Harry could try again.  By then, Malfoy had set up a shield charm over the knot that prevented an easy climb. 

Harry didn't care.  He wasn't going anywhere without that book. 

A crowd had already gathered, chanting and cheering as he paced near the tree. He heard Malfoy's voice. It stood out. While the rest of the students were cheering for Harry, Malfoy was cheering for the Whomping Willow.

Of course, the intermittent cheers of his fellow Gryffindors had transformed into a steady chant of "Potter, Potter, Potter…" The name made his neck itch.

His fingers twitched, ready to climb. Hermione was near him, insistently saying something. But he was already tuning out the voices and concentrating on the tree. He pulled off the robes covering his tattered shirt and jeans. The Muggle clothes he'd found in his trunk were oddly oversized, but robes were not well suited for what he was about to do. Anything that fell free would be destroyed. He set his glasses in place with a sticking charm.

The Willow was already swinging ominously, as if sensing that someone was about to broach its defenses.

Harry bent in a low crouch. The grass was warm under his palm. His arms and legs tensed.

A branch whipped down, tearing across the ground.

Harry grabbed his chance. He took off like a shot. His feet landed on the knobby wood.

The limb flew upward, the wood beneath crackling.

A surge of energy pumped through his veins. He threw his arms out. His hands slammed into the branch, hard.

The Willow flailed. The bough thrashed under his arms.

His trainers skidded off the branch. Harry held on desperately. Rough bark dug deep into his fingernails. His legs scissored through the air, seeking something solid.

From below, another branch crashed toward him. The Willow was trying to flatten him between two mighty limbs.

Harry gulped in air. Steeling himself, he released his hold on the branch. Wind rushed past him as he fell.

The back of his legs hit the branch below.

Pain flashed through his limbs. He contracted his muscles instinctively. His legs curled around the branch and held.

Air whizzed past his ears. He looked up—or rather, down, from his position. The branch was rushing downward. The tree was going to scrape him across the ground like gum off an old shoe.

He yelped, flailing his arms. Catching onto the branch, he scrambled upward. He unwound his legs and clutched the top of the branch in a crouch.

A second later, the branch hit the ground with a sickening thud.

Harry's bones juddered from the impact. He took advantage of the momentary stillness and leapt toward the center of the tree.

The bough turned and twisted, trying to throw him off.

Gasping, he made it several yards. He and the branch were high in the air before he fell again. Several branches crashed against him as he plummeted.

The breath was knocked out of him. He threw his hands out, pushing himself against their movements.

Harry slammed into the crux of the tree.

Scrapes stung his palms. A trickle of sweat dribbled down his aching shoulders. He ignored it, holding himself still. He pressed his hands against the thick branches.

The wooden limbs shifted. He saw his prize. The Potions book had fallen into a small cleft.

Harry inched his way towards it. He stretched out an arm. His fingertips brushed the edge of the book. Straining, he stretched his arm further. He could just barely grab hold of the spine. But Malfoy's hurling spell had been cast with some force; the book was tightly wedged.

The tree swayed sickeningly. The heavy boughs pressed in, closer and closer. Scents of wood and rot filled his nostrils. The sunlight was cut off. Another second and he would be crushed.

Harry wrapped his arms around a nearby branch. Hands and feet scrabbling, he squeezed through a narrow opening. He spied the text below him, within reach.

His legs wrapped the branch in a tight embrace. Harry let go with both hands. His upper body swung upside-down. Reaching out, he grasped the book.

With a wrench, the book broke free. Harry was unbalanced by the movement. His overturned body dangled.

The hold of his legs began to slip.

A horrible constriction closed on his chest, but he clamped down on it. Using every ounce of his strength, he hitched his legs firmly around the branch. He was still gripping the book tightly. His eyes scanned the ground until he saw Hermione, clenching her fists. He shouted a warning and heaved the book at her.

She raised her wand. The book gently floated into her arms.

Relief filled Harry. He allowed himself a grin.

"Let me bring you down, too," Hermione called out, placing the book on the grass next to Harry's discarded robes.

Harry was slightly insulted by the suggestion. Hadn't she seen him climb up the Whomping Willow? Climbing back down was the easy part! He shook his head at her. Tensing his muscles, he pulled himself back into an upright position. He dropped his legs to a lower branch and descended.

He was only halfway down when his hands were yanked from their grip. In a flash, the ground was rushing toward him.

His heart pounded in his ears. He scrambled, clawing frantically at the empty air. He tried to rotate his body. A rolling tumble or a landing on a shoulder was far less painful. But he couldn't shift. He was falling sideways. And then he began to slow.

With a sense of relief, he realized he was being levitated to the ground. He grunted in annoyance at Hermione for ruining his accomplishment.

But it wasn't Hermione who awaited him when he landed with a soft thump. He caught sight of quickly retreating backs as the crowd dispersed. In front of him stood Snape, looking grim.

"Explain."

"Er…" Harry scratched at his sweaty scalp. He glimpsed the text lying next to his crumpled robes. "My book was in the tree."

Snape eyed the book as though it offended him. "And how did that happen?"

"Malfoy."

"You're accusing him?"

Harry shrugged half-heartedly. He was aware of his father's situation. Was there any point in asking him to punish the son of a Death Eater? He viewed the Malfoys the way he viewed end of term exams. He could rant and rail, but ultimately he had to be prepared to suffer through them.

"I fail to understand why you cannot use magic to retrieve objects."

"I did try magic." He didn't regret resorting to physical effort, though. In the past few days, he had been ready to literally climb the walls. Malfoy's little prank had given him a way to work off some anxiety.

"Behaving recklessly for the admiration of a crowd. It's a stunt befitting your father."

Harry looked at him skeptically. A blush crept over Snape's cheeks.

"I meant James Potter."

"Oh." Harry felt the familiar ache of anger and fear at the name, and the curse it carried. Out of habit, his eyes searched the area. But of course it was impossible for his mum to be within earshot.

Snape was scrutinizing him. "What are you looking for?"

The exhilaration from climbing the Whomping Willow abandoned him. "No one. Nothing."

Snape's stare never left him. "I think the last few evenings of term should be spent on potion ingredient inventory, don't you?"

Harry ducked his head to hide his expression, but Snape caught it.

"This is not something to be enjoyed, Potter." He emphasized the last word, which wiped the smile from Harry's face. "This is detention."

Harry nodded and gathered his things, following Snape back to the castle. Climbing the Whomping Willow had worked out better than he'd thought. Still, there was no guarantee Snape would be willing to talk during detention. He cleared his throat. "Sir, since I'll be working with ingredients anyway, could I borrow a few?"

Snape stopped mid-stride and Harry caught up with him. One look at the professor's face told him that his timing could have been better.

"Borrow?" asked Snape

"Well, have," admitted Harry. "I want to help Neville."

"Mr. Longbottom needs to learn the material on his own."

"Oh, it's not about exams. Not directly, anyway. I'm brewing something for his, er, problem."

"His memory?" Snape's brow furrowed. "There is only one potion that I know of for memory."

Harry nodded. "It's too short-term, though."

Snape lifted an eyebrow. "You're developing your own potion?"

"Yeah. I plan on calling it 'The Harry'." He raised his hands at Snape's look. "Joking! It's an existing potion in my world: Memoria Resarcio. It's good for cases of absent-mindedness, where there hasn't been a lot of damage. My dad and I used to brew it for Neville before he learned how to make it on his own." He listed the ingredients, and watched Snape's mind work them over.

"In the right proportions…yes…quite ingenious."

"Don't get a swelled head." Snape frowned at him as they entered the castle. "You invented it. And another potion: Restituomens." Harry felt warm inside just thinking about that potion. "It's more powerful than any other potion of its kind."

Harry noted the slight twitch of the mouth that showed the Potions master was pleased. They stopped at the stairs to Gryffindor Tower. Harry leaned against the wall and examined his fingernails. "I've written down some notes on the potions. We could work on brewing them, if you're interested."

"I’m certain I can discover the correct procedure myself."

Harry kept his face neutral, picking at a splinter under his nail while he waited.

"But I suppose it would save time if…"

Harry perked up from the wall and hopped onto the stairs. "We can do it tonight. See you then."

"Tonight is detention, Potter. It's a punishment, not a school project."

"Just trying to save time." He put a hand on his heart. "I'll try to be as miserable as possible." With that, he left the scowling professor at the bottom of the stairs and dashed to his common room.

At detention that night, Snape set Harry to scrubbing cauldrons. Snape had implied with a smirk that this would be more grueling than potion inventory.

Harry didn't mention that he did both most summers as part of his regular chores. He placed the cleaning fluids and brushes on a table near Snape's workstation, making it easy for the two to talk. Harry was getting a feel for this other dad, as he thought of him. He could sense when the man would tolerate his chatter and when he'd reached his breaking point. As it turned out, he had a very low tolerance.

"I'm trying to work things out with Ron," said Harry. "Hermione says we're best mates, but I dunno…" He adjusted the cauldron in his lap to scrub inside the rim and watched the progress of the potion. "You need to stir in a figure eight pattern."

Snape grunted, hovering over the brew. "Counterclockwise would react better with yarrow."

"Hmm," said Harry noncommittally. When he'd disagreed, he'd gotten bellowed at. When he said nothing and the potion turned lumpy, he'd received a silent glower. Much like the glower he was receiving now.

"You have something to say?" said Snape, gripping the cauldron with both hands.

"Just…usually you start with the basic formula, and make alterations later. I mean, I'm sure you'll find ways to improve it in the future—"

"Don’t patronize me, you insolent child," said Snape, but he proceeded to stir in a figure eight pattern.

Harry scratched at his nose to hide his smile and went back to scrubbing. "Anyway, Ron and I got on well yesterday afternoon, when I let him borrow my…er…broom." He studied the professor out of the corner of his eye. He was entering dangerous territory. "I didn't have a Firebolt in my world."

He saw the lean frame stiffen. "A recent acquisition. One I wouldn't have allowed. Unfortunately, I was overruled."

Harry's heart sank. During the past year, he hadn't received any gifts that were suspected to come from Sirius Black. And if he'd known from the start that the shiny new broom in his possession was from Black, he might have refused it. The two of them had quite a row about his dad the night Pettigrew escaped. But he'd had a few days with the broom before anyone had mentioned their suspicions about the donor. And…it was fantastic. He'd hoped that this world would include a dad who was surprisingly mellow about gifts from personal enemies, but no such luck. "So you'll want me to get rid of it before we go home, then?"

Snape frowned over his potion. "You should get rid of it. But I don't imagine your Muggle family will realize its significance."

Harry's heart slid into his stomach. "My Muggle family?"

Snape's face was impassive. "I believe they're called the Dursleys."

Harry jumped from his stool, the forgotten cauldron clattering to the floor. "Are you joking?"

Snape's hand jerked to a stop over the brew. "Rarely."

Harry struggled for control, but couldn't find it. He slammed his fists on the work table, making the bubbling potion jump. "Why are you sending me to them?"

"I'm not sending you. That is your home."

"It's not my home. None of this is my home. My father would never make me—"

"I am not your father!"

"I bloody well see that now!" As though caught in a gale, the cauldron flew up and smashed against a wall. Harry looked down to see a wand in his trembling hand. He didn't remember drawing it.

He looked up to see that the professor had aimed his wand directly at him.

"Lower your defenses."

Harry did so immediately, but his heart was still pounding. "Why would you do this? I don't understand."

"I've done nothing. You've been told to adjust to this world. Accept that here, we are nothing more than professor and student. There is no further connection."

"Mum is our connection. She always will be."

"Do not speak of her!"

"Why not?" Harry pressed his palms to the table. "Why are you so afraid to talk about her?"

"I am not afraid." His eyes lowered to the table. "She is no business of yours."

"No business?" Harry breathed deeply, trying to rein in his emotions and think rationally. Every time he'd tried to draw the man into a conversation about his mum, he'd been pushed away. "I want to share her with you, don't you understand? I thought that this summer, we could talk. When we talk, she's…not so far away." He sagged onto a stool, his head in his hands. He tried a mental exercise that separated his thoughts from his feelings, but his nerves were too jangled. "I don't suppose you have any bubblefruit," he muttered.

A small, jewel-toned fruit rolled between his supporting elbows.

He looked up in surprise. But Snape's face was so empty that Harry couldn't discern his thoughts.

"I expect that wall to be cleaned as well," was all he said as he directed another cauldron over to the work table.

Harry sighed and picked up his scrub brush, studying the layered stones. The urge to climb the walls was returning. Walls were so much easier to get a handle on.