Percy led the Doctor into a chamber, in which Hades sat on his throne. It wasn't his usual throne room. It was deep, and dingy. Steps led around the edge into a circular cavern, made entirely out of black and grey rock. Hades sat on a black, metal throne, and Percy narrowed his eyes.

"Why is he down here?" he asked himself. The Doctor shrugged behind him.

"Don't ask me," he said. They both continued to creep down the steps, watching carefully as Hades talked to himself. As they got further around the room, Percy noticed a small, portable fountain at his feet. He was speaking via Iris messaging. He listened quietly, trying to find out who he was talking to.

"It's not my fault," he said. His face scrunched up in anger. The person on the other end began talking, but the voice was grainy.

"You have to....don't let....worse than....wait...."the person on the other end stopped talking.

"What?" Hades asked. A shushing sound came, and he asked again in a hushed tone, "what is it?"

"...watched..."

Hades whipped around, and saw Percy and the Doctor before he could do anything. He swiped the message and got angrily up from his chair.

"Jackson!? What are you doing here! And who's the man with you?!" he shouted, flying in a flurry of shadows up the steps, appearing in front of him.

"Er," Percy started, gulping.

"I'm the Doctor," the Doctor said. His face, however, was not happy and cheery. It was cold, like he already had taken a disliking to.

"And you dare to enter my domain?! No! I should blast you into atoms, here and now—" Hades threatened, but the Doctor cut him off.

"Yeah, whatever," he said, "but first, you can tell me why you were talking to a Slitheen." Percy guessed that the Doctor must have had better hearing and sight, because he hadn't even been able to tell what gender the other recipient had been. If it had a gender at all, that is.

Hades fingers curled in fury, and his eyes burned. "I don't answer questions from mere mortals," he hissed. He stepped towards them, and they both stepped back. "It is my business, and my business alone."

The Doctor shook his head. "No, no, it's not. Because you see," he clapped Percy on the back, "my friend Percy's girlfriend has just been kidnapped by them, and suddenly you are consorting with the kidnappers. Now, to me, that doesn't just run by as coincidence!"

Percy blushed again. "We're not a couple! Why does everyone think we're a couple!"

"Nevertheless," Hades growled, "you will tell me how you came to be upon my kingdom—"

"Kingdom?" Percy laughed. Normally, he wouldn't have laughed in the face of an all-powerful, currently furious lord of the dead, but being with the Doctor seemed to give him courage. "It's hardly a kingdom, there's mindless zombies roaming around, with pits of lava and big caves!"

Hades's nostrils flared. "Do not push your luck, Perseus Jackson," he snarled. He stepped forward.

Before she could fall into the burning lava below, a hand flew out of no-where and grabbed her. Donna groaned, as she and the hand-bearer struggled to pull her back up onto the rock. Once she was safely back on... ground, she looked at her rescuer. She was wearing jeans and a Camp Half-blood T-shirt, like Percy. Her blonde hair was untidy, and she had stormy grey eyes like she Donna had never seen.

"Thanks," she breathed, looking cautiously at the bubbling liquid below. The girl nodded.

"Welcome. It wouldn't do to let one of my rescuers be incinerated," she said. Donna wondered if she was actually being serious.

"And, er, who are you?" Donna asked. At any other time, she'd happily sit down with this girl and discuss local matters. But now, her hair was scraggly, she was quite grubby, and her rolled-up sleeves showed marks where she'd been bound.

"I'm Annabeth," she said. Donna eyes widened.

"Annabeth! We're here to rescue you!" Donna exclaimed, almost excitedly. Annabeth raised her eyebrows, in a fashion that said I believe that has already been established.

"Right," she said. There was a rumbling sound, and the ground shook.

"That'll be the Doctor," she said. Annabeth frowned.

"Who?"

"Erm," she said. "I'll explain later. This sort of stuff kinda follows him around." She led Annabeth around near the front of the building, but still, the guard was standing right in front of the doors. "We need to get past him," Donna said. Annabeth nodded.

"Just watch me, er..."

"Donna."

"Just watch me, Donna," she said. She raised a cap, inconspicuously hidden in one of her pockets, and put it on her head. Donna would've scolded her for fidgeting with accessories, had she not disappeared completely.

"Annabeth!" Donna exclaimed. She poked the air in front of her, and a startled voice went 'ow!'. "Sorry," Donna apologised. She hid behind the pillar, and watched in amazement as a rock rose of its own accord, and flew through the air. An undignified 'oof' sounded, followed by a crumpling sound. There was a quiet exclamation of "yes!" before Annabeth reappeared, taking of her cap. Donna gaped at it.

"Never leaves me," Annabeth explained, ginning. Donna couldn't help but smile back.

"I need to get one of those," Donna said as they tottered towards the entrance. "Sneaking past mum for a night out would be so much easier..."

The Doctor grabbed Percy and dragged him back up the steps. Hades smiled, and waved his hands. Two skeleton soldiers appeared out of no-where, and grabbed the both of them, holding their hands behind their backs.

"Take them above," Hades ordered. "I'll deal with them later." He looked at them, hate present in his glare. "I've a very important Iris Message to make." As he walked back down the steps, Percy and The Doctor struggled against the soldiers. But despite having literally no muscles at all, they were too strong.

"This way," Annabeth said. She crouched low and peered around the corner, before waving for Donna to follow. Their footsteps echoed annoyingly loudly on the black marble, so they forced themselves to tip-toe.

"How d'you know your way? I thought you couldn't get into the Underworld unless you're dead," Donna asked. Annabeth raised an eyebrow at her.

"I could ask you the same thing."

They ducked down behind a pillar, as three skeleton soldiers in ripped army clothes stomped by. Once the sound of their footsteps had disappeared, they came out from their hiding place.

"Whew," Donna said, feigning to wipe her brow. Annabeth laughed. "But really though," Donna asked. Annabeth's smile dimmed down.

"It was when Percy first got here. Hades had taken his mother hostage, because he thought Percy'd taken his Helm Of Darkness, along with Zeus's Master Bolt. That's their weapons of power," she explained. Donna nodded.

"I know. Greek Mythology was one of the few things I liked at school," Donna said. Annabeth smiled.

"So anyway, Percy got a quest. Me and Grover went along with him, and when we got to the Underworld, we..."

She didn't finish her sentence, because the footsteps of more soldiers echoed from around a corner.

"Hide!" Annabeth said, taking out her Celestial Bronze knife.

"Where!?" Donna hissed quietly, looking around desperately. Annabeth threw her the Yankees Cap.

"Use that!" she told her. Donna looked at the cap, and then back to Annabeth.

"But what about you! They'll see you!" she exclaimed. Annabeth nodded.

"Yes. But I've got a weapon. You don't. And they want me hostage, they don't even know about you. If they've got Percy and this Doctor guy, then you might be our only chance." She winked. "It wouldn't do to give you up."

Donna gulped, and then nodded. Just as she slipped on the cap, her form shimmering out of sight, the skeleton soldiers marched around the corner. The front line stopped when they saw Annabeth, the rest of them bumping into each other from behind. At once, they raised their swords and charged at her, making clacking and clicking sounds as the stomped. Annabeth raised her knife to try and disarm them, but she was soon overpowered.

Donna wanted to help, but she knew that Annabeth was right; she wouldn't be able to do anything against them. It was best to just stay quiet, and find a way to help later. She watched as Annabeth was dragged away, and swore that she was looking right into Donna's eyes. She winked, before she was dragged around the corner, and out of sight.

Somewhere along the way, Percy and the Doctor had been knocked out. Percy woke up; he was sat on the floor, with what felt like cold metal manacles around his wrists. He tried to pull away his arms, but the chains restricted him from moving them further away than his knee. He looked around, and saw that the Doctor was also next to him. He was chained, but it looked like he'd already woken up. Before Percy could say anything, he whispered "shhh."

The Doctor nodded towards something behind Percy, and he had to bite my lip to stop himself from gasping when he turned. Annabeth was being chained by the skeleton soldiers, and they both pretended to be unconscious as she was dragged over to them.

After a few moments, when they walked away, Percy hissed Annabeth's name. She groaned, but then her eyes fluttered open. She breathed in deeply, and tried to pull her arms in, but found that she couldn't due to the chains.

"Annabeth!" Percy whispered. She looked around, before noticing that Percy was right next to her.

"Percy!" she exclaimed, but then looked around. "What are you doing here!"

Percy smiled. "We came to rescue you, Owl Head," he explained. The Doctor raised an eyebrow.

"Owl Head?" he asked.

"Long story," replied Percy.

Annabeth smiled. "Well thanks, Seaweed Brain. But it doesn't look like we're gonna be getting out of here soon." She caught sight of the Doctor. "I'm guessing that's this Doctor person?"

The Doctor grinned. "That's me. But if I could just get my Sonic Screwdriver, I could undo these chains, but..."

He trailed off, as Hades strolled into the room. Percy only noticed now where he was – he was in Hades's main throne room. It looked almost the same as last time, but there was a wall of rocks and skulls piled high on one corner.

Hades saw him looking and grinned wickedly, tapping his nose.

"Good to see you again, Jackson," he spat. His eyes burned, and he turned to Annabeth. "Ah. Good to see you back, after that little escapade earlier," he snarled, striding over to his throne. He then turned to the Doctor as he sat down.

"You're Hades, I presume," said the Doctor. Hades smiled.

"You presume correctly," Hades replied. He turned to Percy. "Smarty-pants, this one," he said, gesturing to the Doctor.

Percy rolled his eyes. "Why don't you just let us go, Hades! What's with these chains!"

Hades sighed, as if bored.

"Oh, dear Nephew..." Hades said. Percy blinked – it sounded strange having the lord of the dead calling you nephew.

"What do you want?" the Doctor said. His raised voice said he hadn't quite got the gist of 'all-powerful-lord-of-the-dead'. Hades chuckled.

"Wouldn't you like to know?" he said. The Doctor said nothing, and his facial expression remained the same. "You know," Hades continued, "the Slitheen did warn me about you."

The Doctor stiffened. If the Slitheen were indeed fraternising with Hades, thing's didn't look good at all.

"Yes, I understand you've had past encounters with their race," Hades said. He drummed his fingers on the throne's armrest. "Let me guess – what are they doing, with me? Is that what you're thinking? I bet it is."

The Doctor rolled his eyes. Percy gulped, his throat dry.

"What are you doing with them, then?" Percy asked. Hades smiled.

"Like I'm gonna tell you," Hades replied. Percy gritted his teeth.

Hades waved his fingers at two guards who had come into the throne room. They nodded, then clunked away. Hades got up from his chair, and went over to a glass globe in the corner of the room. Inside, shadows and smoke shifted around. Annabeth took this opportunity.

"Doctor!" she whispered. The Doctor leaned forward.

"Yes?"

"It's Donna. She's got this—"

She didn't finish, because Hades turned around and saw them talking.

"Hey!" he shouted, walking calmly back over to his throne, "I didn't ask for you to talk."

Annabeth bit her lip in thought, before a mischievous, 'I just had a marvellous idea' look took stage on her face.

"Hades," she said.

Hades looked from the Doctor, to her. "What?"

"You know your helm of darkness, thing?" she asked. Hades raised his eyebrow.

"What about it?" he asked.

"Well, it's a bit like my hat, isn't it?" she replied. Hades laughed.

"No, Annabeth. My Helm of Darkness is over 1000 times more powerful. Your petty little cap can merely make things invisible. My Helm—"

"Yes, I know," Annabeth cut in. Percy and the Doctor were now looking at her wondering what she was getting at. "But still, a hat that makes people invisible. It's gotta look good, right!" She looked at Percy and the Doctor, like they had a wisp of an idea of what she was talking about. "But I mean, it looks especially good on people with ginger hair, don't you think?"

She glared at the Doctor, who finally understood what she was getting at.

"But you'd have to be careful. If you couldn't see yourself, you might not be able to see where you're going. You might, I dunno... walk into some rocks, for example?"

She looked at the pile of rocks where, quietly, a tiny pebble bounced down the pile, and landed with a small 'tap' on the floor. Hades didn't seem to notice.

"Ah, yes," he said, "I see your point. But whilst we're talking about accessories..."

Hades got comfortable in his chair, knowing that this would last for quite a long time.

"...you know what I like? I like shoes, gloves, and coats— don't get me started on coats! D'you know why?" he asked. Annabeth shook her head. Percy didn't know what was going on, but he shook his head nonetheless, for save of ripping the little charade to pieces. "Because, Annabeth, unlike wedding dresses, coats have pockets!"

He grinned at them. Annabeth nodded, but now she wondered whether the Doctor had gotten the wrong idea, and that they were actually discussing clothes.

"Yeah, um..." she said. She gave a thumbs up, and glanced worriedly at Hades. The Doctor gave her an 'I'm working on it!' look.

"What I mean, is, you can put things in them, like... oh, I dunno. Watches. Sweet wrappers..."

He glanced over at the pile of rocks, raising his eyebrows.

"Screwdrivers."

Donna followed the skeleton soldiers silently, tiptoeing after them after a few seconds of waiting. She watched as they turned around into what looked like a large room. She crept up behind them silently, and found that it was actually much bigger than she first thought. She bit her tongue, stopping herself just in time from walking into a pile of rocks – that level of noise would've been enough to alert the others to her presence.

She hid around the corner, listening to them talk. She could hear the Doctor:

"What do you want?"

A deeper, more evil sounding voice replied, "wouldn't you like to know."

Donna waited for a while, listening to them speak. Apparently, they were all lined up, bound by metal chains. She tiptoed inside the room, and crouched quietly by a boulder. She decided that she'd watch them, unseen, until she saw an opportunity to do something.

Annabeth started talking about her Yankees cap. Donna prodded it cautiously on her head, checking it was still there. Yep.

"...but it looks especially good on people with ginger hair, don't you think?" she said. Donna perked up – that had to be her. "But you'd have to be careful," she continued. "If you couldn't see yourself, you might not be able to see where you're going. You might, I dunno... walk into some rocks, for example?"

Donna gulped. What did that mean? She acted on impulse: she reached out, and lightly prodded a pebble. It tumbled down the pile, and spun quietly onto the floor. If Hades noticed, he didn't let on.

"Yeah," the Doctor carried on, "and whilst we're talking about accessories, you know what I like? I like shoes, gloves, and coats— don't get me started on coats! D'you know why?" he asked. Annabeth shook her head. "Because, Annabeth, unlike wedding dresses, coats have pockets!"

Donna bit her lip to stop herself from gasping. That was definitely a code – the Doctor was trying to talk to her. She remembered their small argument when they first met:

"No," Donna snapped at the Doctor, "it doesn't have pockets! Who has pockets in their wedding dress? Y'know, when I went to my dress fitting, it's funny, 'cos the thing I forgot to ask was GIVE ME POCKETS!"

The Doctor winced. "Who's this guy you're marrying?"

Donna smiled. "Lance."

The Doctor nodded. "Good luck, Lance."

"OI!"

He must want her to do something. She listened as he carried on.

"What I mean, is, you can put things in them, like... oh, I dunno. Watches. Sweet wrappers..."

He glanced over at Donna, and she swore that he was looking her right in the eye.

"Screwdrivers."

At once, Donna knew what to do. She tiptoed away from the rocks, minimizing her noise by 100%. Hades waved his hand in annoyance, just as she reached down into the Doctor's pocket, grabbing the Sonic Screwdriver.

"Enough, enough. I get virtually no time above the Underworld as it it," Hades snapped, "I'm not familiar with all these... things! And no, stalling won't work. We're just waiting for the Slitheen to get themselves over here..."

As he spoke, Donna used the Sonic to undo all of their chains. The Doctor motioned for them all to keep their hands behind their backs. Donna was about to creep away again, when she was grabbed by two skeleton soldiers. She gasped – how could they see her?

Hades grinned.

"Yes, Miss Noble, I can see you."

Donna's mouth hung open, speechless. Hades just laughed.

"You should know, as I said earlier, my Helm of Darkness is over 1000x more powerful than you flimsy old cap. Its mere presence cancels out the effects of such an item." He grinned wickedly. "Anything and Everything from the Underworld will be able to see it."

Before anything else could be said, the ground shook violently. The Doctor, Percy and Annabeth stumbled to the floor, having been resting on their knees. Dust flitted down from the ceiling, and a harsh green light began to glow from the centre of the room.

"What is that?" Percy shouted. A hissing, groaning sound filled the room – it was so loud, Percy had to shout over the noise.

Hades eyes were wide open, staring at the intense light.

"It can't be!"

A/N: I'm SOOOOOOOOOO sorry it's been so long since I've updated! But rest assured, the fourth and final part will be satisfying.

Just a thought: I have a few ideas for a full on fic, but I dunno if I should go ahead with them. What do you think? Please review!!!!!