It's small at first. A small touch, the occasional brush of a hand, so small in fact that Yaz doesn't register why each accidental touch sends her heart into a frenzy. All she knows is that she can't get enough.

The Doctor is one of the most affectionate people she knows; she's always throwing compliments out to her fam, and shows no reserve with her pride in her team. Yaz smiles to herself when The Doctor encourages Ryan after he's done something well, or when she admonishes Graham for his constant hunger. Her smile turns megawatt when The Doctor's affection is directed at Yaz, much to the chagrin of Ryan.

'Yaz was brilliant. The way you dealt with that sergeant was amazing. Five points to Yaz.' Yaz blushed and smiled, returning The Doctor's grin. Ryan rolled his eyes good-naturedly.

'And what about my points?' He asked. The Doctor moved her gaze from Yaz to Ryan, tutting.

'Honestly Ryan, you sound like my son. When you take down a sergeant, you'll get five points.' He threw his hands up in the air.

'No fair. Yaz only gets points because she's the favourite.' Yaz blushed, about to respond to the accusation when The Doctor responded:

'Yeah you're right, she is my favourite.' The Doctor turned to face Yaz and gave her an exaggerated wink. Yaz didn't think she could turn any redder. Her heart was thudding away in her chest. She knew it was a joke, but it still touched something in her. The Doctor's huge smile softened for a moment, her gaze lingering on Yaz. Their eyes were locked, hazel eyes searching brown. Graham then interrupted.

'What about me? As the adult here, maybe I should award my own points.' The Doctor laughed.

'You're the adult? Graham, you get grouchy when you're hungry. I've never heard someone complain as much as you when we're on an adventure! Are we there yet Doc, is this a good idea Doc, Doc I'm hungry. It's like travelling with a toddler!' Ryan was biting his lip to stop himself from laughing. Graham scowled at him. This set Ryan off.

'Oh my god, she has got you down Graham!' Graham harrumphed, arms folded across his chest. He turned to look at Yaz, who was giggling behind her hands.

'Come on Yaz, you're the voice of reason. Tell them to stop bullying me!' She shrugged apologetically.

'Sorry Graham, but you're the grown up. Fight your own battles.' Graham muttered something about ungrateful youths under his breath, whilst the rest of the team laughed. Out of habit, Yaz glanced at The Doctor and found she was already looking at her. She smiled affectionately, and Yaz's heart started thundering harder against her ribs. Why did that keep happening? The gaze lingered yet again, and Yaz could feel her face heating up.

'Is it me, or is it really hot in here?' She said suddenly, feeling overwhelmed by the intensity of The Doctor's gaze. She flicked her eyes down to the console, away from The Doctor, focusing on anything else. She tried fanning herself in an effort to calm her reddening cheeks. The Doctor's brows furrowed, concern setting in.

'Are you alright Yaz?' She strode across to Yaz, her hand coming to rest on her forehead. As soon as her hand came into contact with Yaz's forehead, Yaz felt a jolt throughout her entire body, as if she had been shocked. The Doctor pressed forward, getting into Yaz's eyeline. 'Yaz?'

Yaz squeaked and jumped back, away from The Doctor's cool hand.

'Yep, fine. How about another adventure? I think we should go somewhere really, really cold. What d'ya say?' She spoke quickly, trying to change the subject. She had her hand on the main lever, waiting for the others to agree with her. The Doctor was still looking at her, confusion and concern written all over her face, before her expression changed again.

'Good plan Yaz, let's go somewhere cold.' She paused, then her smile returned. 'I know just the place!' She dashed about the console, bashing buttons and turning dials before coming to Yaz's side. She paused, before placing her hand on top of Yaz's. Yaz felt that jolt again, as warmth spread throughout her hand and up her arm. She glanced up at The Doctor, who was already looking at her. 'Ready?' The Doctor asked softly. Yaz nodded, confidence returning.

'Ready.' Together they pulled down the lever, and the entire console room flooded with light, whirring into life.

'Where are we going?' Graham asked, leaning against one of the columns. His glance flickered between The Doctor and Yaz, who hadn't moved from their positions. Their hands were still clasped together on the lever. The Doctor looked over at him, smiling.

'Somewhere awesome,' she beamed. Yaz chuckled. The Doctor's enthusiasm was infectious. The whirring stopped and the console room was silent. They'd landed.

'Right team, it's going to be freezing outside so you'll need to wrap up warm. Head to the wardrobe and grab a coat.' The boys started heading in the direction of the wardrobe, whilst Yaz remained where she was. The Doctor still hadn't released her hand.

'Where are we?' Yaz asked quietly, breath coming out short. When had The Doctor got so close? They were standing hip to hip, the points of contact causing warmth to blossom up the rest of her body. The Doctor looked down at her, an amused smile spreading across her face.

'Like I said, somewhere awesome.' She gave Yaz's hand a slight squeeze, before letting her hand slide slowly off the lever. 'Now off you pop, you've got to get wrapped up.' She moved away from Yaz, allowing her space to go. Yaz immediately felt cold without The Doctor next to her. Reluctantly, she nodded at The Doctor and went to find the boys in the wardrobe.

Graham and Ryan turned to look at her when she entered the wardrobe, already wrapped up for the adventure ahead. Yaz laughed out loud at Ryan who had his fluffy hood up over his head.

'You're not outside yet Ryan,' she jested. Ryan stuck his tongue out at her.

'You're just jealous I've got the best coat.'

'No, I'm jealous that you've got the best coat. The Doc didn't specify how cold it'll be, but knowing her it'll be arctic levels of freezing.' Graham complained. He had a warmish looking coat on, but it had no faux fur trim on it. Ryan countered cheekily.

'Beauty before age Graham, beauty before age.' Graham's face fell in shock.

'Ryan Sinclair, you have the cheek to…' He was cut off when Ryan bounced out of the room. 'Can't hear you under this warm hood!' He called out down the corridor. Graham sighed, returning to putting his scarf on. Yaz reached out to one of the coats, then slipped it on. She hadn't noticed Graham watching her until she turned around to do up the zip. She looked up, and caught his concerned expression. Oh no, not him too!

'Are you alright Yaz?' She could feel her face heating up again. She hated being the centre of attention. She looked away from him, searching for some gloves to put on.

'Yeah I'm fine Graham, just felt a bit hot is all.' She purposely kept her face turned away from him, but she could feel his eyes boring into her back. Trust Graham to play the Granddad with her too. It was lovely that he cared, but right now she just wanted the ground to swallow her up.

'It's just, you seem a bit on edge. You were pretty jumpy back in the console room.' Oh crap, he'd noticed too? Thinking of a quick lie, she turned around and said:

'I think it's just the adrenaline from our last trip. Just need to get it out.' She squeezed his arm in thanks; thanks for recognising that she wasn't alright, but for trying to help anyway. She was about to leave the wardrobe and head back, when Graham piped up:

'Y'know, Yaz, If you need to talk about anything, you know you can come to me right?' Yaz stopped in her tracks, stuttering:

'Really, Graham, thank you but I'm fine-'

'I know, but in case you weren't, I just want you to know that you can. If you need too.' Yaz was flabbergasted. She didn't know what to say; Graham really was the best Granddad. It was a shame Ryan didn't always see it.

'Thank you. I appreciate that.' She smiled at him and he returned it, before finishing up with getting ready. Yaz left him to it, and headed back to the console room.

She took her time wandering back, thinking about what she was feeling. She was jumpy, yes, but she didn't know why. She had been full of adrenaline earlier in the day, but now she had recovered from that adventure, she knew that wasn't where her energy was coming from. She felt wired, excitable, and nervous. But why? There was no threat now, no danger. She thought back to when she started feeling uncomfortable. Or was that even the right word? Not exactly uncomfortable, but not relaxed either. Definitely nervous. And this wasn't the first time she felt like this either. Since she had met The Doctor, her entire emotional state had been an array of nerves, constant excitement and contentment. She was the happiest she had ever been in her life. But she was also the most anxious. It dawned on her. Anxiety. That's what she was feeling, right? She thought to herself, sure, anxiety is part of it, but the label didn't feel quite right.

Before she reached the door of the console room, her stomach did a somersault. She could hear The Doctor laughing with Ryan, and her heart warmed with affection. The Doctor's laugh was melodic, beautiful even, especially when it was caught off-guard. Taking a deep breath, Yaz entered the console room.

As soon as she entered, Ryan glanced in her direction, smiling. The Doctor had her back to her, her body still shaking with laugher from whatever Ryan had been saying.

'Alright Yaz, where's Graham?' Ryan asked, looking behind her to see where he had go to. The Doctor turned, and her smile grew when she saw Yaz had returned. Yaz returned the smile, before moving her gaze to Ryan.

'He's just coming, sorting out his gloves I think.' Graham appeared behind her, fully wrapped up and ready to go.

'So where are we Doc?' The Doctor shook her head, and moved towards the front doors.

'Not telling, it'll ruin the surprise. Come on!' She waved them over and headed out the doors. The three companions looked at each other before following her out.

The first thing that struck Yaz was that it was freezing cold. It wasn't snowing, but it there was a thick layer of snow on the ground that crunched beneath her feet. Yaz loved the snow, ever since she was a little kid. She smiled to herself, looking down at her feet as she made footprints. She looked up and she could see Ryan was doing the same thing, and she laughed. He looked up at grinned back at her.

'Hey Yaz, remember that snow day back in primary, when I got that snowball down Mrs Burns' top?' She laughed at the memory.

'She was so mad at you. Didn't she make you stay behind to write lines?' Ryan nodded.

'She did indeed. But it was totally worth it.'

Graham coughed to interrupt them.

'Doc, the snow is lovely and everything, but why are we here? Where are we?' The Doctor, who had moved behind them as they had made their way out of the TARDIS, grinned wickedly.

'Always with the questions. Just, look up.' Together they looked up at the sky. Yaz's jaw dropped. Swirling blues and greens waved across the open sky, likes gentle crests of the ocean. They shimmered across the vast inky blankness, like a reflection.

'Is that what I think it is?' Graham asked, astounded. The Doctor grinned.

'Yes, it's the aurora borealis. Also known as the northern lights. It's pretty rare to see them, and the conditions have to be just right.' Yaz kept looking at the sky, mouth open, taking it all in. Her neck started to strain a little, but she didn't care. She could feel The Doctor move closer to her side, her arm brushing against hers.

'I've always wanted to see them. I never thought I'd get the chance.' Graham said, sounding a little sad. Ryan looked over, knowing he was referring to Grace, and his previous illness. Ryan nudged him.

'You're here now. That's the main thing.' Graham gave his grandson a grateful smile.

'Very true,' he murmured. The Doctor looked over at Ryan, who had returned his gaze to the sky.

'What do you think Ryan?' He looked over at her, grinning excitedly.

'It's sick, Doctor. I've never seen anything like it.' He paused. 'Aren't the northern lights meant to be gateways to other universes or something?' Yaz turned to look at The Doctor, expecting her to come back with some witty retort or sciency explanation. What she got instead shocked her. The Doctor was looking sadly at the sky, and in that moment she looked impossibly old.

'If only,' she replied quietly. She didn't have tears in her eyes, but they looked glassy, like she was remembering something from long ago. Something heart-breaking. Yaz suddenly felt like she was intruding on a private moment. But, looking at The Doctor's sadness, she had to do something. Carefully, she brought her hand down and brushed it against The Doctor's. Her fingers nudged gently, cautiously against The Doctor's. Tentatively, she felt The Doctor respond, digits slowly bumping against each other. Fingers danced around each other slowly, quietly, before becoming interlaced. She was still looking at the sky, but at least she was grounded back in the present. Yaz let out a soft sigh she hadn't realised she'd been holding. She turned her attention back to the sky.

She could sense Ryan and Graham's discomfort at The Doctor's shift in mood, but remained silent as they turned their attention back to the sky. The silence went on, but started to become more comfortable, communal. They watched it with reverence, each lost in their own thoughts.

The Doctor's hand was in hers more solidly now, as she seemed to return more fully to the present. She squeezed their joined hands, and in turn Yaz squeezed back, reassuringly. You're not alone in this, she wanted to say. Instead, what she murmured was:

'It's so beautiful.' She felt The Doctor divert her gaze away from the sky, and look at Yaz fully. Yaz kept her eyes resolutely on the sky, feeling her heart begin to pump at an alarming rate. There was that nervous feeling again. Like she was about to skydive out of a plane. Then she heard The Doctor whisper.

'Yes, it is.' Yaz turned to look at The Doctor, and found her looking right at her. Yaz's breath caught in her throat, and felt her cheeks warm again. The Doctor gave her a small, affectionate (loving?) smile. It was the most sincere she had ever seen The Doctor. She then felt The Doctor lean in closer by her side, breaking the silent barrier that seemed to have developed between them. The entire right side of Yaz's body was on fire. Everything felt so impossibly hot, but also so right. Then The Doctor dropped their hands and brought her arm to rest around Yaz's waist. She pulled her even closer to her side, not wanting to let go.

Yaz stiffened, holding her breath. The Doctor felt her stiffen, and something flashed across her face momentarily. Hurt? Confusion? Yaz wasn't sure. However, she quickly reassured The Doctor by relaxing into her grip, letting her know that it was okay, welcomed, wanted. The Doctor smiled, relieved. She tightened her grip a little, hand coming to rest in Yaz's pocket. The Doctor slowly lowered her head to rest on Yaz's shoulder. To make them more comfortable, Yaz brought her hand up to wrap her arm around the blonde, mirroring her actions. Her head rested against the top of The Doctor's head. She could smell The Doctor's scent radiating off of her, and tried to repress the urge to inhale too deeply. It was intoxicating. They stayed connected, warm, and continued to look at the sky.

Out of nowhere, a snowball came flying into their faces, causing the lovely contact to cease.

'Come on lovebirds, time for some snow fun!' Ryan had pelted the snowball at them, grinning as he could see he had hit his targets. Yaz felt her face flush again, and rubbed the freezing particles out of her eyes. Ignoring his comment, Yaz shouted:

'Ryan, I'm so gonna kill ya.' She crouched down, scooped up some snow into her gloved hands and made a snowball. She looked up, aimed at Ryan and took fire. He dodged out of the way just in time, and taunted her.

'That the best you got Khan?' By her side, The Doctor recovered from the snowball and had created her own snowy ammunition. She bowled and hit Ryan square in the chest. He looked up at her in shock. He had tried to dodge her, but she had been quicker than him.

She cheered as she hit him, and held up her hand for Yaz to high five her. Yaz very happily obliged.

'Bring it Ryan. Just be warned, I won the best snowballing competition on the planet Deuxus 6 years in a row.' Ryan rolled his eyes playfully, rubbing the snow off his coat. He then threw his hands up in the air when he saw The Doctor reach down for more snow.

'Okay, okay, I believe you! No more snow!' The Doctor grinned, carefully and slowly letting the snow fall from her hands. She chanced a look at Yaz, which Yaz caught the end of, before turning her gaze back to the boys. She glanced at Graham, who had turned his head back to the sky. She could see the wistful look on his face; she knew exactly what he was thinking about. She made her way over to him, standing by his side, and resumed looking at the sky.

'What causes them, Doc?'

Knowing what he was referring to, she said:

'When a coronal mass ejection collides with the magnetic field, it causes complex changes to happen to the magnetic tail region. These changes generate currents of charged particles, which then flow along lines of magnetic force into the Polar Regions. These particles are boosted in energy in Earth's upper atmosphere, and when they collide with oxygen and nitrogen atoms, they produce that dazzling auroral light.' The boys turned to her in confusion.

'And…in English?' Ryan asked, bemused.

'Basically lots of charged particles collide with atoms high up in the atmosphere, which causes the beautiful lights up the sky.' Yaz explained, looking up at the sky. The entire group looked at her in awe. The Doctor's eyes seemed to be sparkling.

'Yasmin Khan, you never cease to amaze me.' Yaz looked at her directly, mouth slightly agape. The Doctor looked so… proud. She averted her gaze, blush creeping up her cheeks.

'What can I say, physics was my favourite subject at school.'

'Why, was it because Mr Jones taught you?' Ryan nudged her shoulder playfully, causing Yaz to turn even redder. Who knew she could blush so much? At Ryan's jest, Yaz could see The Doctor's smile falter, ever so slightly. Or was that her imagination? Yaz elbowed Ryan in the stomach, trying to shut him up.

'No, of course not. I just love science.' Ryan, however, didn't take the hint.

'Sure Yaz, sure.' He patted her shoulder mock-comfortingly. 'I heard all the girls fancied him.' God Yaz wanted to hit him. She brushed off his hand.

'Well, what about Miss McKenzie? I bet you only took Art because she taught it.' Ryan smiled, not fazed by her rebuke.

'Yep, and I don't deny it.' Graham's face fell in shock at his Grandson.

'Ryan, you didn't?!' He admonished. It was now Ryan's turn to be embarrassed, momentarily forgetting that he wasn't just with the boys. Yaz smiled at Ryan's spluttering, and caught The Doctor's eye. For a split second, The Doctor looked like… Yaz wasn't sure. Disappointed? Hurt? Sometimes she could be so hard to read. But as soon as Yaz caught her eye, she gave her a small smile, some of the warmth returning. Yaz was relieved. Suddenly, The Doctor pulled her gaze away and back on the boys, clapping her hands together.

'Right, I think it's time for our next adventure. Back in the TARDIS you lot, it's getting a bit chilly.' The group looked at each other, a little confused at The Doctor's abrupt change in mood, but didn't question it. The boys led the charge, talking between them. Yaz hung back with The Doctor, feeling slightly uneasy. Although The Doctor was fairly laidback, when her mood changed it sometimes gave Yaz whiplash. The worst thing was, she wasn't sure what had caused it. One minute she'd looked so happy, but now she looked unsure, and had gone quieter. It was never good when she did that.

Not sure what to say, Yaz did the only thing she could think of in that moment. She hooked her arm through The Doctor's, so that they were arm in arm. The Doctor looked at her again, startled by the contact. She glanced down at their interlinked arms, then looked up at Yaz and smiled again. She pulled Yaz closer to her side, and put her other hand on the top of Yaz's pro-offered arm.

'Thank you,' she whispered gently. Yaz's heart started thumping against her chest again, not sure why The Doctor was thanking her. However, not wanting to knock it, she whispered in return.

'You're welcome.' She felt The Doctor squeeze her arm in response, as they headed back to the TARDIS. The way Yaz's heart was thumping, The Doctor might as well have reached into her chest and touched her soul.