The obsession had started when she was a child.

She watched them from afar, the wings, the tiny, wiry legs, the fluttering and flitting of the butterflies as they flew about in the open air. Her first butterfly had been injured, a wing missing a tip and she'd taken it back to her family cottage to feed and nurse.

It had passed.

It was only then that she started catching them as caterpillars, watching them spin themselves into cocoons, then hatch into butterflies. She inevitably cried when she watched them fly away, inexplicably jealous that such a graceful, delicate creature that the ability to fly free.

She believed she could do the same.

Med school had been a chance and she'd taken it willingly. She was smart, not just pretty, and truly believed she could make a difference. Holding her butterfly pendant around her neck and knowing the butterfly clip was securely holding back her bangs, she stepped into school confident and excited.

Feeling like she had the wings of freedom.

Her husband had damaged her wings. She didn't resent him for it, not in the slightest. He couldn't help his cancer, couldn't stop himself from dying and she didn't hate him for it. It taught her a lot about bedside manner and about patients. It also taught her a lot about herself, what she could and couldn't handle. Her heart had grown a cocoon and hardened again.

Her obsession tapered substantially.

Foreman had been the first of her Princeton colleagues to find out about her butterfly obsession. They'd taken to spending one night a month doing something, both of them understanding the bond they shared as surrogate siblings. It had been four months into her fellowship and they'd finally chosen her apartment to hang out in. His Christmas present had been a new butterfly clip.

It boosted her love.

Wilson was next, then Chase, though the latter finding out was something she preferred to forget. Wilson had put two and two together, finally noticing the one constant in her attire. The butterfly glinted from somewhere, and he started his own game at finding each day's pick, pointing it out to her when he found it. It never ceased to make her laugh. He'd given her a rare framed butterfly as a present when she quit.

She'd remembered why she loved their grace and beauty.

She wore the same necklace once a year for a month, the month that her husband had passed, and it was well into her third year before House took notice. By that point, she'd quit, returned, and grown a backbone. He'd been shot, dealt with his ex, and realized a whole lot about what he wanted from life. She smiled shyly and blushed when he complimented her on it, Chase and Foreman off doing doctor things and she researching what she could for their case. Then she'd stuttered when he sincerely asked about her obsession. She hadn't thought he'd noticed.

Butterflies began to show up in the office, on her desk.

A year later, their first Valentine's Day as a couple and one of the holidays she knew he hated, he surprised her with a thin black box. Opening it, she revealed a new necklace and a set of earrings. The card was simple, nothing hearts and no undying declarations of love.

Time for a new one.

She couldn't bring herself to throw out the one she wore for her husband, but had asked him to watch as she buried it in the bottom of her jewellery box before asking him to help her with the new one. He dropped a soft brush of lips to her neck as he finished, arranging her hair back over her shoulder blades.

He'd asked her why she loved them so much.

There was no way she could explain the feeling she'd had as a child, watching the butterflies fly off into the distance. There was an untameable grace to them, a simple way that made her wish she could be as unburdened as they were.

He simply wrapped her in his arms as they drifted to sleep.

She wore the pendant the next day, and the day after that, and the day after that. She wore the pendant the day he proposed, wore it the day of their wedding – he'd surprised her by releasing butterflies to the sky at sunset as they kissed for the first time as husband and wife – wore it the day their daughter was born, and the day she was promoted to Head of Immunology.

She never took it off.

She played with it on bad days, her fingers brushing over the metal and gems to calm her raging nerves or her rage in general. He watched her hand gripping the pendant as she stood on the roof, coming from a yelling match with him over the treatment of a patient he'd asked her to consult on. He didn't hesitate to limp over to her, resting a hand on her shoulder. She faced him and he noticed the earrings for the first time, the same one's he'd given her ages ago.

Today was a bad day.

He held her close, feeling her arm between them and one hand brushing the edges of one of her earrings. He didn't apologize and neither did she, both of them aware that the things they'd shouted were truth and barbed. He pulled back after a moment and put a hand over hers, on the pendant. She smiled.

"I love you too."