Ruby's stomach twisted into knots at the confession from the other Ruby in the room. She couldn't quite fathom what she'd just heard, and it was even harder to believe that she, of all people, could have done something like that. It was overwhelming, and she held up both hands in a gesture of surrender while taking a few steps backward. "Hold on. I don't understand." Restlessness overtook her; she wanted to run away, get out of the Tardis, and leave the Doctor if it meant she could keep him safe. "I don't understand any of this."

The Doctor ignored her for the moment and turned to Future Ruby. "What happened?" There was no judgement in his voice, only a curiosity-driven question.

Ruby couldn't grasp it. Surely he would be furious with her—he must be. Her future self had just revealed that she had killed him. Her mind raced, and her heart pounded in her chest.

Future Ruby appeared anxious but began to explain in a relatively steady voice. "We were trying to rescue the Aelorian people, who had been captured. The Tardis received their distress call and took us to the location where they were being held."

The Aelorians were known for their scientific intelligence and innovativeness. It made sense that they had developed a machine capable of manipulating time and dimensions, considered the Doctor.

''When the coast was clear and the Zenthari - who had captured them,'' she added, ''were at a safe distance, you used the sconic to enter the building where the Aelorians were held captive.''

Current Ruby noticed the first real sign of emotion on the Doctor's face as soon as her future self uttered the name 'Zenthari'. She witnessed him shaking his head and clench his fists, his eyes darkening.

''Who are they, the Zhentari, Doctor?'' she asked hesitantly.

''They are ruthless predators,'' he explained through gritted teeth. They prey on your deepest and darkest fears, purely for pleasure. And once they figure out what those fears are, they infiltrate your mind and impose them upon you.''

Ruby swallowed back the lump that had formed in her throat. ''How do they do that?''

The Doctor tugged at the sleeve of his jacket, considering his words. ''They manipulate the mind. Are masters at it. They can show you whatever they want, so vividly and realistically that that you can't tell it's not real. They do the worst kind of mind tricks.'' He then gestured for Future Ruby to continue.

The girl nodded. ''You told me about them and what they could do before we went in, but I think that we'd both underestimated their reach,' she went on. ''Even though they weren't physically there, they apparently manipulated our minds from a distance. Only, we didn't realise that this was happening until it was too late.''

'Interesting', the Doctor thought to himself. The Zenthari must have strengthened their powers since his last encounter with them.

''You suddenly decided that you had to inspect the time machine, which was in the same building,'' Future Ruby went on. ''So, that's where we went first. And that's where it all went wrong.''

Current Ruby closely observed her future self, still freaked out by the whole thing, and wondered if she'd always looked so vacant when traumatised. She presumed it was the shock her future self was feeling that brought this on. Without further thought, she moved closer to the Doctor and took his hand. No matter what Future Ruby would reveal next, she wanted to support the Doctor as much as she sought support from him.

''You just took one look at the machine and came to the conclusion that it was faulty, and that you had to stop it before the whole planet would explode, taking everyone with it,'' Future Ruby continued.

''Let me guess,'' the Doctor interjected. ''That was an illusion. There was nothing wrong with the machine, was there?''

Future Ruby nodded, confirming the Doctor's suspicion. ''You were shouting about smoke coming out of the machine, blinking red lights, and all sort of alarming things. But I didn't see anything. The machine was just standing there, idle, you know? Nothing moved, no noise, no smoke, no lights… I tried to tell you, but you didn't listen. It was like you were under some sort of spell. You pushed me away, told me to run, to get as far away as possible.'' She paused. ''Then you aimed the sonic at the machine and switched it on. I think, in your mind, to try to stop it from exploding.''

Current Ruby gripped the Doctor's hand even tighter, but he kept his eyes steadfast on Future Ruby, encouraging her with his big, dark eyes to resume telling the events of her past and their future.

The girl took a deep breath and stared down at her feet. ''The next thing I knew, I had this sudden strong urge, like knowledge, that I had to stop you from manipulating the machine. It was strange. I don't know what came over me. But looking back, it was probably the Zhentari's influence manipulating my mind. I was fully conscious and knew exactly what I was doing, but I was also convinced at the same time that I was doing the right thing. But what I did was actually disastrous.'' It was like she only now found time to reflect, and think thoroughly about her actions. ''I pushed you aside and tried to grab the sonic from you, but when I did, I think I changed the settings of the sonic or something, because everything started to happen all at once.''

Her voice sounded genuinely shocked, although there was also a hint of composure that Current Ruby didn't quite recognise from herself. Then again, she had never had the chance to observe herself as a spectator up close, so perhaps this was just how she spoke. Either way, she needed to know what happened next, no matter how terrifying the story became. ''What happened? Ruby, what did you do?'' she asked her namesake, while holding her breath.

''There was an enormous bang and I'd never seen such a bright light. It came from the machine, at least that's what I though at first. But then out of nowhere, you, Doctor, were lifted up from the ground and flying. Really flying! And only then I noticed that you were the one the bright light came from, not the machine,'' Ruby's gaze fell. ''I tried to pull you down, but I couldn't, and you wouldn't respond when I called your name. I think you were unconscious. Everything happened so quickly…'' She tucked a strand of hair behind her ear repeatedly. Twice. No, three times, the other Ruby noticed. A nervous habit she didn't realise she had.

The Doctor had told Ruby of regeneration, explaining that this happened to him when was mortally wounded, changing his face but not killing him. She remembered telling him not to change his face, and his promise that he would keep this one for a long, long time. She swallowed back the tears that stung behind her eyes.

While Ruby felt miserable and anxious, the Doctor sounded almost excited. ''Ah, time-machine-induced regeneration!'' he exclaimed, as if solving a favourite puzzle. ''A powerful one. Heard of it, but never experienced it. Not until in the near future, clearly.''

Future Ruby had told the Doctor that this time, it wasn't just regeneration, but that he'd had truly died - something Current Ruby wasn't yet aware of.

''What happened next?'' the Doctor asked.

The older Ruby's shoulders slumped, and tears started to stream down her face. ''The Zhentari happened.''