Fred was legitimately concentrating in Potions that afternoon, he was doing his best to avoid talking to George about Evan.
Aside from his mother, the thing Fred was most afraid of was being serious. That's exactly how things had gotten between he and Evan; serious. He had yelled and screamed and acted like a complete twat in front of a girl was seriously into him… and he was seriously into her… and that was scary. Sure, he had been with a few girls before, but it was all fun and games. Evan was different; she had a career and made him talk about his career and what he wanted in his future. He wanted Weasleys' Wizard Wheezes and that's all he knew so far.
When the time had come to talk about George's accident in a serious manner, he had exploded. He didn't really remember what he had said in the heat of his anger, but George had told him he had ripped into her for not being sensitive enough and not having experience with family. Fred felt horrible and had been avoiding Evan at all costs; nothing more serious than apologising for being a twat.
While he was rationalising his thoughts, 'she doesn't want to talk to me any way, not after what I said…' he didn't notice George float a small amount of howling harpie hair into his growth potion. Moments later, the entire cauldron overflowed and spilled over Fred, making his skin turn bright purple.
George hid sniggers as Professor Snape glided over to where Fred was sitting and clock him over the back of the head.
"Hospital Wing Weasley," he drawled monotonously, "Detention for a week. Tonight."
Fred sighed, cursing what he thought was his own absentmindedness, and headed out of the dungeons; hoping it was Evan's day off.
Rounding the corner, Fred smelled the 'Hospital Smell' and the all too familiar Raspberry undertone.
'Damn it,' be cursed, 'she's here.' Knowing he couldn't walk around being purple for the rest of his life, Fred took a deep breath and walked into the Hospital Wing.
Evan was sitting on the chair at her desk, scribbling something in a book.
"Bleeding, oozing or broken?" Evan said irritably. Fred didn't say anything for a moment so Evan spoke again, "Well?"
"Stained." Fred said softly.
"Fred?" Evan gasped, looking up from her book and directly into his eyes.
"Hi." He replied lamely, "I had an accident in potions."
Evan walked around her desk and swiftly up to Fred, slapping him squarely on the jaw.
"I deserved that." Fred said, following Evan further into the Hospital Wing where she pointed at one of the beds, indicating it was for him to sit on.
"You're damn right you did." She grabbed her wand angrily and pointed it at him.
"Whoa," he said scrambling off the bed and attempting to hide behind a curtain, "I don't deserve that."
Evan rolled her eyes, "You don't deserve it," she agreed, "but I'd sit down and let me do my work unless you want to stay purple the rest of your life."