Relationships never ended well for Claire.

She'd dated all throughout her school years and residency. She had a few high school girlfriends after she'd come out in sophomore year. She'd been an idiot teenager, and had no clue what she was doing. Each relationship burned fast and bright, extinguishing after a couple of months.

During medical school, Claire was so stressed and focused on soaking up all she could that she had no time for serious relationships. She had a few dates here and there, but they rarely amounted to anything other than casual hookups throughout the school year. Then, once she'd reached residency, things had calmed down a little and Claire started to reconsider her standing on serious relationships.

Her longest relationship had been with Serena. Nearly two years. A few years older, a bit more experienced, and a hundred percent Claire's type. She was the first woman who'd heard the words "I love you" come out of Claire's mouth. It was the first time Claire had allowed someone to get close enough so that they could really hurt her. And hurt her she had. To say it had ended badly would be an understatement.

The point was, Claire had no trouble with getting women in bed, and that wasn't just her being immodest. Maintaining commitments was where she fell short. She was dedicated to her job, and that clashed with her personal life. She worked long hours, prioritized her work over her girlfriends, and was terrible at remembering anniversary gifts. After countless dates and angry breakups, Claire had come to the realization that maybe relationships weren't for her.

Claire knew all of this.

So why couldn't she stop thinking about her neighbor?

Her mysterious, aloof, incredibly attractive neighbor who was always up and jogging in odd hours of the morning. Who would disappear and come back with grievous injuries, refusing to go to the hospital. Who had faint, white scars covering her entire body, some barely noticeable and some that hadn't healed so well. Who was clearly stronger than she looked, by the way she'd cracked her fist over that mugger's face, over and over, her face a storm of calm fury.

Claire wasn't stupid. She knew something was off about Natasha. The woman radiated a dangerous aura. She had the body of a dancer, lean and muscular. Her eyes were unusually sharp and intelligent. She moved so silently and stealthily that her footsteps barely made a sound on her nice hardwood floors.

But it wasn't just physical. It was the way her green eyes would study her surroundings reminded Claire of a coiled-up snake, waiting for the right moment to strike. It was the way she held herself. She was only an inch or so taller than Claire, but when Natasha looked at her a certain way, she seemed to be towering over her. Every movement from her was deliberate and calculated, like she was following the steps of a carefully choreographed dance sequence.

Everything about Natasha screamed that she was not one to be messed around with, yet Claire couldn't help but be drawn to her. She liked her dry humor, which flared out at the most unexpected of times. She liked her wry smile and her confidence. And she was a badass.

The night of the mugging, Natasha had taken her back to the apartment and told her to get a good night's rest. Claire had no intention of doing such a thing. She cleaned her injuries up, then flopped into bed. Her body was aching and begging for sleep, but her mind was awake and alert. The mugging had shaken her, but what kept her awake was that red hair, those green eyes.

Not feeling particularly sleepy, she checked her phone to make sure Natasha's contact was still there. She couldn't help but smile like an idiot again, giddy at the memory.

However, it was quickly replaced by a twinging anxiety. What was the texting etiquette here? Natasha had been the one to give Claire her number, forcing Claire to make the first move. Clever woman. Did that mean they were officially kind of friends? Or did Natasha give her phone number for emergencies? She should at least clarify who she was.

Claire opened a new text chain, typing in Natasha's contact. Her fingers hovered over the keyboard as she grasped for something to say. Something witty? Something flirty?

She settled for Hey neighbor.

She read over the words three times, imagining them being said in different inflections. It was safe. Safe and boring. It looked like she hadn't put too much thought into writing it. She added a smiley face, then hurriedly deleted it. Before she could change her mind, she hit send.

This is Claire, she added quickly. She sent that too and felt a little ridiculous after. Of course it was her. What other neighbors had Natasha given her phone number to? She fell back on her back, phone on her stomach. Not wanting to see the result, she closed her eyes and tried to convince herself that she didn't care if Natasha responded or not.

God, she was turning into a teenager.

Barely a minute had passed before her phone buzzed with a new message. Despite her insistence that she didn't care, Claire's eyes snapped open and she made a wild grab for her phone. Self-restraint be damned. Heart accelerating in anticipation, she read the message.

Natasha: You're still awake, I see

Claire: couldn't sleep. Did i wake you up?

Natasha: no

Natasha: Did you ice your injuries?

Claire sent the eye-rolling emoji. I think you keep forgetting that I'm a doctor.

Natasha: is that a yes?

Claire: Yes

Natasha: Good. wouldn't want you to bruise your pretty face

Claire: you really think it's pretty?

Natasha: I'm not blind

Claire bit back a smile as she stared down at her phone. She was sure that Natasha was flirting with her. Pretty girls flirting with her always made Claire a little cocky, so her next text was fueled by a rush of boldness.

Claire: I'm going running tomorrow. Want to join me?

A minute passed. Only a minute, but it was a long one that seemed to stretch and pull the longer Claire waited for a response. She turned off her phone and blew out a sigh, not bothering to hide the sinking feeling in her stomach. Sure that she'd blown it, she started to practice the breathing exercises that would calm her down as she drifted to sleep. Two breaths in, her phone buzzed again.

Natasha: you sure about that? I'd destroy you

Claire: I can hold my own

Natasha: we'll see about that. name a time and place

Claire: 8 a.m.. meet in hallway

Natasha: prepare to be destroyed

Claire: it's a friendly run, not a competition

Natasha: definitely not, because I plan to win

"Morning," Natasha greeted as Claire stepped from the warmth of her apartment into the freezing cold hallway. She was sipping on a coffee. Her breath made wisps in the air. "You're late."

"I'm on time. You're early."

Natasha displayed the time on her phone. Claire rolled her eyes.

"Okay, I'm three minutes late. Happy?" Claire glanced at her coffee. "You had time to go to Starbucks? Do you ever sleep?"

"I could ask you the same thing."

Claire tried to be subtle about the once-over she gave her. Natasha was wearing her workout clothes again, yoga pants and a simple tank top. Her hair was straightened that day, smooth and silky. It was tied back in a braided bun. The muscles on her arm flexed when she raised the cup to her mouth. No wonder she was so strong.

Obviously Claire hadn't been as discreet as she thought, because Natasha said, "Take a picture. It'll last longer."

Claire went for a nonchalant shrug. Don't you dare blush again. "I can't help it. You know you're hot."

Natasha seemed to like that. "Flatterer." She stepped a little closer and studied Claire's face. "You bruised."

Her pain was a reminder of the mugging. Claire had tried to hide the angry dark blotches on her face with concealer, but she'd only been partially successful. Her jaw still ached from the blows, and she could still taste the blood in her mouth, even after she'd rinsed multiple times. Her face twinged when she talked.

Claire tried not to flinch as Natasha raised a hand to graze her cheek. She smelled like vanilla perfume and coffee.

"Does it hurt?"

"No," Claire lied. "It's just a couple of bruises. They'll fade in a couple days."

Natasha leaned back. Claire felt a twinge of disappointment at the loss of contact.

Claire nodded to her outfit. "You're not even going to take a jacket? It's pretty cold in the morning."

"Russian winters are nothing compared to this."

"You're Russian?"

"I grew up in Stalingrad."

It made sense, given Natasha's bone structure and coloring, but her voice held no trace of an accent. Claire filed it in her brain, something pleasant blooming in her chest as she received another fleeting piece of information about Natasha.

A smile curled Natasha's lips as she took in Claire's outfit. "You're pretty bundled up."

"I hate running cold."

Claire wore a long sleeve under her old college hoodie and gray sweatpants. She'd tucked her blonde hair under a beanie. She had her hood up and her hands were clenched into fists inside her sleeves already, trying to preserve the little warmth she had. A handheld water bottle was strapped to her hand. Next to Natasha, whose sleek clothes made her look like she belonged in a Nike commercial, Claire looked like a homeless man.

Natasha finished her cup and binned it. "Do you have the day off?"

"My shift starts at noon."

"Good. Then we have plenty of time." Natasha smiled. "I wasn't lying about planning to win."

It was even colder outside. Claire shook out her numb limbs to warm herself up. They started off at a light jog, heading towards Central Park. Claire felt a rush of energy as her sneakers thudded on the pavement. Running was her personal caffeine. She'd been working nonstop, but it'd been a few days since her last run. She felt renewed and strong as her legs carried her across the streets.

Her breath went in and out, the frigid air attacking her lungs and sending a rush of adrenaline through her. Her arms moved steadily at her sides, in rhythm with her step. The beat of her heart was steady and quick. She knew her form was perfect, molded by the criticism of her coaches and the hours in practice.

Natasha was matching her step for step, letting her set the pace. Their strides were about the same length. Claire had been jogging fast enough to work up a sweat, but Natasha wasn't even breathing hard.

Claire slowed when they reached the park. Natasha stopped next to her. Claire looked at her expectantly, trying to slow her breathing. "What's the route?"

"Follow me."

Natasha set a brisk pace as she led them through the main paved route. The new pace was closer to a run than a jog, faster than Claire's had been. They passed other runners, families walking, couples hand in hand. The sun was out, and the frigid air had become a cool breeze on Claire's skin. She lowered her hood.

As they jogged past, Claire noticed that she was getting some strange looks from passersby. The bruises on her face probably incited questions.

Natasha turned onto a running trail. Claire was familiar with it. It was her least favorite to go on because it was hillier than the other ones, a four mile loop that went around the rougher parts of Central Park.

"A full loop around, then rest?" Natasha suggested.

Claire nodded.

There were significantly less people on the trail. It was blissfully peaceful as they made their way down the first loop. The only sounds were the muffled voices of people through the trees, the pounding of sneakers on gravel, and the chirping of birds. Claire was warming up under her hoodie.

Claire managed to keep up with Natasha for the first few miles, but it irked her that she was always a half-step or so behind. It seemed that every time she caught up to Natasha, Natasha would quicken her pace again. Claire swore she saw Natasha smirk after the third or fourth time.

When they passed the three-mile marker, Claire's breathing was ragged. She was regretting wearing so many layers.

"Having trouble?" Natasha asked innocently, slowing to a jog.

"Not really," Claire managed, her voice betraying her.

"You're breathing pretty hard."

"Isn't that the point?"

Natasha let out a short laugh as she picked up the pace, passing Claire once again. Claire's competitive streak flared up, making her adjust her speed as well. She darted ahead of Natasha and slowed once she was a couple inches in front, looking over her shoulder to flash a smug smile. Natasha retaliated by lengthening her stride, pushing off the ground in graceful arcs until she was just ahead of Claire.

They continued their little race, each trying to get the upper hand until Claire was sprinting as fast as she could. By the time they reached the fourth mile, her heart was going crazy. There was a stitch in her side and her legs were burning. The breaths she took were quick and shallow. They didn't seem to be reaching the bottom of her lungs. Claire was satisfied to hear that Natasha's breathing had gotten more desperate as well.

Claire could see the beginning of the trail, where they had started, in the distance. All thoughts of passing Natasha had dissipated. She knew she didn't have a chance of beating her. Claire had fallen a few steps behind, but she was determined to finish strong. She could think of little except the need for air and the muscles in her body screaming for rest.

When she passed the ending point, she all but collapsed on a patch of grass. Her chest heaved for air. She could feel her heartbeat throughout her entire body. Her entire body was blazing with heat.

Natasha was watching her with an amused smile.

"Don't," Claire gasped out between breaths, "say a word."

"I wasn't going to say anything."

"Yeah, right."

Claire yanked off her beanie and pulled her hoodie over her shoulders, throwing them onto the ground. Her long sleeve was completely soaked through. She didn't hesitate before ripping that off too, leaving her in a simple running bra. The cool air relieved her blistering skin. She closed her eyes in relief and sighed.

"Next time, I'm wearing a…" Claire trailed off when she noticed Natasha staring at her midriff. She wasn't even trying to be subtle.

"Take a picture," Claire said, tossing Natasha's words back at her. "It'll last longer."

Natasha's eyes snapped back to her face, but she didn't blush like Claire would've. Completely unabashed, she raised an eyebrow at her. "You're the one who's stripping in front of me."

"I'm hot," Claire protested.

Natasha smirked. "Yes, you are."

Her heart nearly stuttered to a stop. "Huh? I, uh—"

Natasha laughed.

"You're the worst."

She helped Claire to her feet. "C'mon, let's get you some clothes. I'll even buy you a coffee as a consolation prize."