Yaz and Martha left the restaurant, happier and fuller than when they had entered. Their friendship was back on the road to recovery, and even Yaz had managed to eat a small amount of food.

They decided to walk back to the TARDIS, given that the night was clear and they wanted to walk off some of the pizza. Mickey had informed them that the tracer still needed a couple more hours, so the two women started the walk back.

Since their reconciliation, they hadn't stopped talking. Swapping notes on their Doctors, filling the other in on adventures they had been on, and monsters and people they had met.

'Okay, how about Shakespeare? Have you met him?'

'Oh yeah, I met him alright.'

'No way! What was he like?'

'Very flirty.'

'He sounds like fun!'

'Oh, he was…'

'Martha! You didn't?!'

'No, of course not! Although, he was quite insistent…'

'Maybe he wrote a sonnet about you.'

'He did!'

'Shut up!'

'I'm serious… Will, that old flirt!'

Yaz was seriously impressed.

'Okay Martha, I'll give it to you. Being chatted up by Shakespeare is beyond cool.'

'Well, what about you? Who is your favourite historical encounter?'

'Oh that's easy. Gotta be Rosa Parks.'

Martha stopped in her tracks.

'Hold on. You've met Rosa Parks. The Rosa Parks?'

'Yeah. She was awesome.'

'I bet she was! Damn, I'm so jealous. I should have suggested her to The Doctor. She's like, my hero.'

'Well, maybe you can. When we get her back and all.'

Martha stopped, and turned to look back at Yaz. Surprise and hope were emblazoned across her face. She looked at Yaz, smiled, and then turned to look back across the city. The lights twinkled amongst the darkness of the evening. Silence fell between the two women. Yaz wondered what Martha was thinking.

'Travelling with The Doctor. It's such an adventure. It's a great life. The best life. I've often wondered what would happen if The Doctor came back into my life. I left her, but I don't think anyone can ever really leave The Doctor.' She paused, glancing back at Yaz. 'I've got a son, you know.'

Yaz's widened in surprise.

'You do?'

'He's called August. Just turned 5.'

'He sounds adorable!'

'He's the cutest.' Martha sighed, turning back towards the city. 'I don't get to see him as much as I'd like. Well, what we'd like. Mickey tends to work from home these days, perks of the job as a hacker. But still, when I'm out in the field, I'm torn. I'm doing a job I love. I couldn't imagine doing anything else now. And then there's my little boy, and I have to decide whether I'm being fair to him.'

'Fair to him?'

'I want to be a good mum to him. I try my best. But then, the job calls. The adventure, the independence, the thrill. I'm juggling trying to mother my son and saving the world. It's not easy.'

'Martha, I bet you're the best mum ever. I bet his friends are super jealous of his cool mum!'

'Yaz, you're kind. I can see why The Doctor likes you.' Yaz couldn't help but blush.

'I'm just pointing out the obvious.' Yaz walked towards Martha, and stood side by side with her. 'Would you want to travel with The Doctor again?'

'In a heartbeat.' Martha glanced at Yaz. 'But not permanently. I've always had my family to look after. The Earth needs someone to defend it. I think Mickey and I are the last of the old lot left, and I couldn't just leave it all behind…'

'Martha, I think you're forgetting something.' Martha looked at Yaz in surprise.

'What's that?'

'The Doctor has a time machine. You could go anywhere and still be home in time for tea.'

Martha laughed, then grinned at Yaz.

'Oh Yaz, you do know The Doctor right? Not exactly the most reliable driver.'

'Tell me about it. It took her several attempts to drop us home before we travelled with her full time.'

'Maybe she just didn't want to let you go.' Martha mused.

'What, that early on?'

'The thing about The Doctor is, Yaz, is that she always needs someone to travel with. To hold her hand. To hold her accountable. To keep her sane. That's what our job is. By the time she met you, she must have been alone again, for whatever reason.' Martha paused. 'Maybe she looked at you and saw the chance of a fresh start. To be happy.'

Yaz looked down at the floor. She hadn't really thought about how lonely it must be when you are thousands of years old. Who had travelled with her just before Ryan, Graham and herself? How long had she been alone? Had she been alone when she died and regenerated? That must have been a terrifying experience.

She turned her attention back to the sky, trying to hold back the tears. All she wanted was for the daft old alien to come bounding up behind her and launch into one of her rambling speeches. Her chest ached with longing. She missed her so much.

Martha caught the sadness on Yaz's face, and moved closer to her. She seemed to debate internally as how to comfort the younger woman, when she decided to tear down their walls, by putting her arm around Yaz's shoulders. Yaz didn't even flinch. Martha was completely forgiven.

'We're going to get her back, Yaz. I promise.' Martha whispered into the dark night. Yaz knew in her bones that Martha meant every word of her promise.

'No you won't.'

Breaking out of their reverie, Martha and Yaz spun round to be confronted with their stalkers. Yaz's eyes widened in horror.

'Darryl? Trisha?'

Yaz hadn't seen The Doctor's attackers since they'd vanished from their house days before.

'Good to see you again, PC Khan. It's going to make what's coming to you all the sweeter.'

Well, threats were never good. Martha, sensing the hostility rising, immediately stepped in front of Yaz.

'And what's that going to be?' Martha asked confidently, not about to let two bullies attack her friend.

'Martha Jones. I'm surprised you're even here.'

'How do you know my name?' Martha asked, less confidently, but still standing her ground. Yaz tried to take a step forward, but Martha held her back in place.

'We know all about those that associate with The Doctor. Although, it's been some time now, right?'

'What do you want?' Martha asked, deflecting the question. Yaz pulled at Martha's back, trying to whisper something desperately in her ear.

'Martha, they attacked The Doctor and I a few days back. They stabbed her with a huge needle and took some of her blood.'

Darryl and Trisha shared amused glances with each other.

'That's right, PC Khan. All that fighting you did back at the house was for nothing.'

'Why not?'

'Because we've got The Doctor in our grasp. Well, our masters do. And we're gonna reap the biggest rewards.' Trisha said gleefully.

Yaz felt her stomach fall out from beneath her. Darryl and Trisha had succeeded in their mission, and now The Doctor was suffering because of it. White, hot rage boiled up from within her. She made to leap forward, but she was held back yet again by Martha.

'You bastards, where is she?!' She yelled at the two perpetrators, who were just laughing at her pain.

'Oh Yaz, you won't get anywhere with that temper. We have secured The Doctor for our masters, and we get to live out our lives in luxury.'

'What does that mean? What have you taken her for?' Martha asked, trying to keep her own anger down. Now was not the time to ignite the fire.

'For money, obviously.' Darryl interjected. He clearly wasn't the brains behind the operation.

'So, what, you're selling her?'

'Yeah, for riches and a chance to start a new life.'

'What are you selling her for?'

'The masters wanted her specifically. Apparently she's the answer to longer life.'

'Longer life?'

'I dunno, something to do with her blood. It's anti-ageing.' Trisha paused, and looked at her husband. 'We're gonna be rich and young forever, aren't we love?'

Martha and Yaz looked at each other in horror.

'You're testing on her?!'

'Well, we aren't. We've done our bit. Well, most of our bit.'

'Where is she?' Yaz called out desperately. Trisha just laughed, as Darryl took a step forward.

'You're never going to see her again. She's in a highly secure facility, where scientists and the masters are working together for the ultimate solution.'

'The solution to what?'

'That's not for you to worry about. Because we've still got a problem we need to take care of.' Something in Trisha's voice let Martha and Yaz know that they were the problem to be eradicated.

Martha glanced between to the two potential assailants. Darryl was thick-set, strong, with his skin-head attitude and leering demeanour. Trisha was slight, but her determined expression showed she was a fighter. Her long, silver necklace, glinted under the harsh lights of the streetlamps. It was the only delicate thing about her. They might not be easy to take down, but Martha had faced worse. They weren't exactly Daleks.

She decided to try The Doctor's method first. Good old fashioned debate.

'How did you find us?' She asked, trying to deflect their attention away from Yaz.

'We've had our eye on The Doctor for a while. It's taken a few near misses to find her but eventually we got lucky, when we found out Yaz was in the police. Then it was just a matter of time.'

'Near misses?' Yaz asked, confused.

'Well, we weren't going to find her on the first go. We're not stupid. We knew she frequented the Sheffield area. We needed to expand our sample range, so we tested a few people. Some were sent up for further testing, but they never came back as a match.'

Yaz's mouth opened in horror.

'The missing people, you took them? Where are they now?'

Trisha shrugged.

'What else do you do with the trash? Take it out.'

Horror flooded Yaz's veins. She could almost feel her dinner come back up, so much so that she had to turn away in disgust. She couldn't believe how blasé the couple were about the savagery that had been afflicted against their own people. How their complicity had led to the deaths of innocents.

'How could you do that?' She asked quietly, not being able to look them in the eye. She didn't want to see their smug looks. They couldn't be human.

'It wasn't hard. We're part of a team of humans who were recruited. At the end of the day, people are expendable.'

'Aren't you human?' Yaz asked, flabbergasted.

'We are human. But we work for the masters.' Darryl interjected.

'Who are the masters?'

'They're aliens. They're going to make us rich and let us live forever.'

'How?'

'We captured The Doctor. They're using her blood to create ways to be immortal. We're getting the biggest payout…'

'Okay, that's enough of that. We need to know where our friend is… perhaps we could come to some sort of arrangement.' Yaz looked at Martha in alarm. What was she doing?

'Sorry love, there's nothing you have that we want. But we've got orders. Orders that involve getting rid of the evidence. Oh, and by the way, you're the evidence.' At Trisha's words, Darryl moved even closer to the two women, already towering over them.

'Where's The Doctor?' Yaz asked, more angry than scared now. Anger, horror and panic were fuelling her. She could not get the image of those poor people out of her head. How scared they must have been. How scared The Doctor must be. Trisha laughed at her again.

'You can ask as many times as you want, I'm not going to tell you.' She paused, taking in Yaz's anguish. 'But what I can tell you, is that your friend, she's not going anywhere. They're just going to keep testing on her, using her, keeping her in a lab until she's no longer useful. At the end of the day, she isn't important.'

This time Martha could not hold the whole force of Yaz back behind her. Yaz stepped around her new friend and took strides towards Trisha. Darryl tried to intervene, but he wasn't quick enough for her. Yaz launched herself at her adversary, letting out a scream as her fist made contact with that smug face.

Trisha stumbled backwards in surprise, holding her wounded nose.

'Darryl, do something!'

The next few seconds were a blur. Yaz felt herself be pushed to the ground, away from her nemesis. Her head met the concrete with a slam, her head shuddering from the force. Her vision blurred alarmingly. She could only make out colours and shapes moving as she forced her eyes open. She could feel blood trickling down the side of her head, onto the harsh ground. Her ears were ringing from the impact, and all she could hear was the scuffling of a fight. She was pretty sure she had concussion, but she had to keep going. Martha needed her.

Taking a couple of seconds to attempt any kind of recovery, Yaz pushed up from the ground, stumbling back to her feet. To her left, she could sense Darryl and Martha were locked in battle, but her vision was still swimming. Meanwhile, she could make out a figure pelting towards her. That had to be Trisha.

Trying to buy herself some time, Yaz staggered to the side, rather than in the opposite direction, trying to distract her opponent. Come on Yaz, let your training kick in.

Her vision was coming back, but her head was ringing. Yaz would just have to fight through the pain. Trisha let out a growl of frustration as Yaz side-stepped her, then turned towards her angrily.

'There's nothing you can do. You're going to die today, Yaz. Unable to save that Doctor of yours. Such a shame. She was such a pretty thing.' She paused for effect. 'But you saw that already, didn't you?'

Yaz took a deep breath, not rising to the bait. She needed to clear her head, needed to make sure she was in a position of strength. Look for Trisha's weaknesses. Yaz analysed her opponent again.

Trisha was slight, yes, but could pack a punch. She was perhaps the same height as Yaz, so she wouldn't have that over her. Yaz reckoned she weighed more than Trisha, so if she could topple her she should be able to pin her to the ground. After all, she had once before. Granted, she'd been in her uniform, but this couldn't be too different.

Trisha whipped out a knife from her pocket, and that instantly changed the game. Yaz was surprised she hadn't got the weapons out earlier. She was holding the knife in her left hand, and was pointing it towards Yaz. This left Trisha's whole right side exposed. Yaz guessed (and hoped) that Trisha would think Yaz would go for the knife first. Yaz's next actions depended on that assumption.

She barrelled herself towards Trisha, as fast as she could. As she approached, she kicked out her leg to hit Trisha's right knee. Her foot made impact, hard, which caused Trisha to launch forward with the knife, in an attempt to protect herself and stab Yaz. As soon as the knife came forward, Yaz used her right hand, pushing it upwards against the outside of Trisha's hand. She slapped the hand, hard, and the knife went flying sideways, out of harm's way. Trisha buckled, allowing Yaz the chance to overpower her. Yaz tripped her, flipped her and sent her sprawling to the ground.

Trisha smacked to the ground, but that didn't stop her fighting back. As she went down, she tripped Yaz, causing the girl to fall to the floor too. Before Yaz could react, Trisha had pinned her to the ground. Hands were at her throat, and Yaz couldn't breathe. Trisha's enraged eyes glared down at her. She really was set on killing her. Yaz had never seen that level of animosity, even in some of the wickedest aliens she'd met.

Yaz scrabbled at Trisha, trying to push her away desperately. The only thing she could grab was the long silver chain that had been hanging from her enemy's neck. Yaz yanked it, in an attempt to distract Trisha. Instead, it came off in her hand, away from the original owner's neck.

As soon as Trisha realised this, she panicked.

'No, no, you can't take that!' Her hands unclasped from around Yaz's neck, and Yaz used her opportunity to escape. She kicked up from underneath Trisha, causing the other woman to wince. Clearly the pendant was important. Finally, she had leverage.

She slapped Trisha from beneath her, and kicked her weak knee again. This time, Trisha howled. Suddenly, her attacker was off her, knocked sideways. Yaz took that as her opportunity to get to her feet, before her opponent had the chance to recover.

Martha suddenly hovered above her, holding out her hand.

'Quick, Yaz, we haven't got much time.'

Yaz took the proffered hand. Martha pulled her to her feet, and together they surveyed the scene. Darryl was knocked unconscious (how Martha had pulled that off, Yaz had no idea), but Trisha was still conscious. They could take her, but she was ruthless.

Yaz still had the pendant in her hand. Trisha saw her look at it, and glared at her.

'Give that back!'

'Why? Is it important?'

Trisha got to her feet, glancing at the ground for the knife she'd brought.

'I'll kill you if you don't hand it over right now.'

Yaz handed the pendant over to Martha, who was looking at it closer. It was just a simple silver locket, sitting on a long silver chain. Yaz was watching Trisha warily, with whom they had reached an impasse. She wouldn't be able to reach for the knife with the two of them watching.

'You and who's army?' Martha asked assertively. Yaz felt relieved by her friend's tone already. Trisha screamed in frustration.

'That's dangerous, hand it over now!'

Martha was examining the locket now, and a smile came across her face. Yaz didn't know what she was thinking, but she felt comforted by that smile.

'I'll tell you what, Trisha. You tell us where The Doctor is, and we'll hand this over.'

'Never!'

'Well, okay then, we'll just keep it then…'

'No, no, wait, let's compromise. I can give you information.'

'Good information?'

'Yes, yes, fine!'

Martha purposely linked her arm with Yaz's, making sure the younger woman was connected to her. Yaz didn't know what was going on, but she just followed Martha's lead. She seemed to have a plan at least. Martha turned the locket over and over in her hands, glancing between the necklace and the now desperate Trisha.

'Go on then.'

'The masters are in disguise, they're masquerading down here on Earth.'

'Who are they?'

'I don't know what species they are. They just call themselves the masters.'

Both Yaz and Martha felt a chill run down their spine. They both prayed it wasn't a certain evil Time Lord.

'That's not very useful,' Martha replied.

'They're working with an Earth company, one that specialises in biotech and research.'

'What's the name of the company?'

Trisha glared at them, hatred seething with every word she was forced to say.

'Vivus.'

Martha and Yaz glanced at each other. Yaz had never heard of it, but she saw a flicker of recognition in Martha's eyes. Martha turned back to Trisha, whose hatred was now oozing out of her.

'Well thank you Trisha, you've been very helpful. Maybe we can continue this tango another time. Yaz and I have some work to do.'

'Hand it over, a deal's a deal.'

Martha played with the pendant in her hands, letting the silver chain slip through her fingers.

'Hold on to me,' she whispered to Yaz. Yaz complied, still utterly confused but putting all her faith in her new friend.

'It's been fun chatting, but we'd best be off. Hope you get home safe!'

Before Trisha could call out, Martha opened the locket. Yaz held on tight as blue light encapsulated them. Her eyes closed as the force surrounded her, Trisha's cries echoing around her head as they disappeared from her sight.

In a blink, they were gone.