One after another, Neville, Hermione and Donna left the potion room. Once they were all through, the flames died down. So far so good.

Donna looked at her friends. "I'll go next. If Quirrell is still there, the plan is to keep him there until help arrives, preferably without his being any the wiser. Give me a minute before you follow me so I can drink the other potion." She briefly hugged both of them, wishing she'd thought to do that with Harry too. "Good luck."

As soon as she entered the puzzle room again, the oddly coloured fires started burning again. Hoping she wasn't making a mistake taking the different potions in such short succession, she reached for the smallest bottle and checked it.

It was full.

Allowing herself one moment of relief that she'd guessed correctly, she unstoppered it and drank. Then she turned to the black fire and stepped through, the icy sensation feeling quite similar to the previous time. She wondered if maybe the two potions were the same, but that would be a level of humour she didn't think Snape was capable of.

On the other side of the flames, there was a large circular room, with pillars all around and a central open area. Right in the middle of the open space, with Quirrell standing in front of it, there was that damned mirror Harry had shown her at Christmas.

Harry himself had manoeuvred himself so that the cloak covered everything that Quirrell might see, but he was holding it open towards the door. She managed to slip underneath without their professor spotting her.

Thinking four people would be a snug fit, not to mention impossible to move without making noise, she brought her mouth close to Harry's ear.

"Bring me to a pillar," she whispered with the least amount of air possible, so that the sound would not carry any further than necessary. Quirrell didn't look up, so he hadn't heard her. Good.

Harry nodded once, and together they moved a bit to the right, as quickly and quietly as they could. The pillar was plenty broad enough that she could hide behind it, leaving Harry free to wait for Hermione. Donna noticed you couldn't see the black fire from this side of the door, which was... odd. Maybe the fire wasn't real, but an illusion? Again, she didn't think Snape would play a prank like that, not when he was apparently serious about protecting the Stone, but what did she know?

When Hermione came through the fire, she and Harry repeated the same little dance so she could hide behind the next pillar, and then Neville went over to the pillar on the left of the doorway. After that, it became hard to say where Harry was, since he hadn't taken off his cloak.

Quirrell still hadn't looked towards the door, instead prowling around the mirror.

"Blasted mirror," he was saying, "how does it work? I'm sure it's the key to finding the Stone, but all I can see is myself using it to restore your body, Master."

Ok, so he didn't have the Stone yet. Then it was just a matter of keeping an eye on him, and only intervening if he got close to finding it. If they had any kind of luck, nothing would happen until Dumbledore or another teacher came to their aid, depending on who George could find.

Of course, that thought jinxed it. She'd hardly thought it or a high-pitched voice sounded, coming from near Quirrell, although there was nobody there. Or nobody visible, at least.

"There is somebody in the room..." it said.

Donna's heart skipped a beat. If they were discovered... they didn't have enough magical knowledge between them to defeat a grown wizard, one who was a lot more competent than he'd let himself appear. If there was indeed a second wizard present, they stood a snowflake's chance in hell.

She needed to keep him talking. Maybe if she could delay long enough, he wouldn't realise there were actually four people here. She was the DoctorDonna, she was good at talking!

Just as she was about to give up her position, she felt someone squeeze her hand. The next thing she knew, she was standing with the Invisibility cloak in her hands, and Harry was approaching Quirrell. Curses! Of course, he didn't know about the talking, did he. She'd told him about the DoctorDonna, but other than the Fluffy incident, he hadn't actually seen that side of her in action.

"Harry Potter," Quirrell smiled. Donna saw he even stood straighter than he'd ever done in class. "I might have known you'd be here. You are too curious for your own good."

Without further preamble, he snapped his fingers. The next moment, Harry was tightly bound with magical ropes. Donna gestured to Neville and Hermione to stay where they were. Harry had obviously had the same thought as her, and she didn't want to make the gesture worthless. She could turn this to their advantage.

She wrapped the cloak around herself. If any opportunity to help Harry presented itself, she would be ready to grab it.

"I saw you and Snape, in the forest," Harry said desperately. Good, focus his attention away from the mirror. She listened to Quirrell's reply with half an ear, but she saw her chance. While he was distracted, she quickly went to stand in front of the mirror. She didn't particularly want to see the DoctorDonna being all happy with the Doctor in the TARDIS, but getting the Stone away from Quirrell was more important than any heartbreak she might feel.

It seemed that the mirror didn't care one jot about invisibility cloaks. It sensed her in front of it, and reacted accordingly. At first it reflected only the room, Harry standing bound by the ropes and Quirrell talking to him. Then there it was – the TARDIS, and the Doctor, and the DoctorDonna, as if they were actually here. She had to force herself not to look around. It wasn't real, they weren't here at all. If nothing else, she'd have heard them landing.

The Doctor had a red rock in his hand, which he threw up and down. There was no doubt in Donna's mind that he was playing with the Philosopher's Stone. Then he grinned right at her – oh, that cocky grin that meant he was just about to save the world, only give him five minutes and room to talk.

He threw the Stone at the DoctorDonna, who plucked it deftly from the air – maybe she should try out for Seeker, Donna thought hysterically.

The DoctorDonna looked at the Stone in her hand, a similar smirk on her face. It had taken years for Donna to reach that level of self-confidence again, even if she hadn't known that was what she was striving for. She'd never quite succeeded, though she'd come close. It was the smirk of a woman who knew exactly who she was, and nobody was going to take that from her. She winked at Donna, and put the stone in a pocket.

And just like that, Donna tilted slightly to the left with the unexpected weight of it. She had the Stone. Now she needed to get it out of here as quickly as possible, before Quirrell realised what had happened, except there was no way she was leaving her friends behind.

She quickly left the mirror, so that she wouldn't accidentally bump into Quirrell, and went over to Neville, who was closest to the door. She showed her face. Leaning close, she whispered in his ear. "Take it away. Broom." She gave him the Stone and the cloak, and nodded to the door. Neville nodded grimly, before disappearing under the cloak. She could only hope, and make sure Quirrell didn't realise his prize had just left the room.

Perhaps a quarter of an hour had passed when things went south, as things were wont to do in Donna's experience. Harry had run out of things to ask Quirrell, who had returned to his scrutiny of the mirror. He grew steadily more frustrated, until he finally yelled, "Master, help me!"

The same voice as before answered. "Use the boy... use the boy..."

Oooh... not good. Very not good. If he realised Harry couldn't get the Stone, her friend might get hurt. And where was that voice coming from? If she didn't know any better, she'd say it came from under Quirrell's turban.

Wherever it came from, though, the result of the order was that the ropes helpfully disappeared and Quirrell placed Harry in front of the mirror.

"What do you see?" he demanded.

Harry was obviously thinking fast, squinting into the mirror. "I'm... grown-up, in my seventh year... I'm Quidditch captain, and I just won the house cup... I'm shaking Dumbledore's hand."

Good boy. He obviously didn't want to give away his actual deepest desire, that was just giving your enemy ammunition.

"He's lying..." the voice said. "Let me speak to him... face-to-face..."

That... sounded ominous.

Quirrell protested, "Master, you are not strong enough!"

"I have strength enough... for this."

As they watched, Harry in the middle of the chamber and Hermione and Donna behind their pillars, Quirrell unwrapped his turban. So she had heard that right? The voice had come from under there?

A moment later the turban fell away, and as Quirrell turned around, Donna caught a glimpse of the pale face and red eyes on the back of his head. No doubt who that was, and she'd be damned if she was going to let Harry face him alone.

"Oi!" she hollered, charging around her pillar at the same time as Hermione. "Pick on someone your own size for a change!"

She came to a stop in front of Harry, taking a good long look into the snake-like face of Voldemort. "God," she said, wrinkling her nose, "you are one ugly bastard, aren't ya!"

"What?" Voldemort shrieked. "What's this? Who are... I remember you," he said suddenly, his red eyes narrowing. "You were in the forest. You stopped me drinking the blood of the unicorn, you and your little friends."

Donna curtseyed. "At your service."

"But I am stronger than you thought," Voldemort continued, ignoring her. "Still I continue, even without the blood."

"Pssh, yeah, and such a fun way to exist, pasted to the back of someone's head, always hidden by cloth. Didn't it get stuffy in there?"

"Once I have the Elixir of Life, I will be able to create my own body again, and you will pay for thwarting me!"

"Oh, honey, I've thwarted worse than you, evil you can't even dream of. I defeated a madman who would have erased all of reality. You got offed by a baby. You're not nearly as impressive as you like to think you are."

"Silence! Tell me what you saw, boy, or your mouthy little friend dies. Where is the Stone!"

Quirrell started walking backwards, and so did the three of them – in the direction of the door.

Then Donna started laughing, causing Quirrell's body to stop its backward advance.

"What is the meaning of this?" Voldemort demanded.

"Well, Moldy Shorts, the meaning of this is that the Stone isn't here."

"What? Of course it's here, it's in the mirror and the boy knows how to get it out!"

"No, I don't know that," Harry replied. "What I saw in the mirror was Donna getting the Stone out and giving it to Neville to take it away."

Donna grinned at the bastard. "He's probably with a teacher by now. Whoop! Run!"

The last part was said to Harry and Hermione. Quirrell turned around with a snarl and ran after them with a hate-filled face, while Voldemort shrieked, "GET THEM!"

They actually made it into the potion room, causing the flames to roar back into life. Quirrell managed to grab Harry's hand, causing him to trip and fall. His glasses were knocked askew, but then Quirrell stopped and looked at his hands, which had started blistering.

Harry scrabbled backwards, but before Donna could get to him and help him up, Quirrell seemed to remember for one moment that he was a wizard. She and Hermione were picked bodily up and slammed against the wall. By the time she'd got her breath and her bearings back, Quirrell was on top of Harry, with Voldemort shouting to kill him.

Even as she rushed up to try and free Harry, the man started blistering all over and shrieking in pain. She and Hermione tried to dislodge him, but there was only so much two young girls could do against a grown-up.

And then, suddenly, it was over. Quirrell's body was yanked off Harry's, picked up by a magic not their own. A flash of purple, a hint of emerald, and Donna found herself being carried by a stern witch. She was suddenly dead tired as the adrenalin drained out of her and she realised they were safe.

"Now do you believe us that there's a thief?" she murmured, but if McGonagall answered she never heard it, as she dropped off into a deep sleep.