The Artist ran her sonic screwdriver over Martha's phone. "Right, there we go." she said as she finished, "Upgraded to Universal Roaming. Thought it was about time you had it." She handed Martha the phone back.

"No way! It's too... mad!" Martha grinned, seeing 'Universal Roaming activated' on the screen, "You're telling me I can call anyone, anywhere in space and time on my mobile?!"

"Long as ya know the area code." the Doctor remarked, pressing buttons on the console, "Frequent flyers' privilege."

"Go on, try it." the Artist encouraged Martha. Martha began to dial a number when the TARDIS jolted suddenly, nearly sending her toppling to the floor had the Artist not caught her in the nick of time.

The Doctor looked at the monitor, which was now flashing red. "Distress signal!" he said, "Locking on!" He activated a switch on the console with his foot. "Might be a bit of..."

"Turbulence?" the Artist cut in, "Easily remedied." She pressed a blue switch on the console and the flight became much smoother, then she and the Doctor piloted the TARDIS into land.

"Come on, let's take a look!" the Doctor said, rushing to the doors. Martha ran after him and they stepped out of the TARDIS to see that they'd landed in what appeared to be an engine room, which was glowing red from extreme heat. "Whoa! Now that is hot!" the Doctor remarked.

"Whoo! It's like a sauna in here!" Martha agreed, slipping her cardigan off.

"I've had worse." the Artist remarked, stepping out last. She'd checked the environment on the scanner, so had wisely left her jacket in the TARDIS, having transferred her sonic screwdriver and psychic paper to her jean pockets first.

"Venting systems." the Doctor observed, looking at pieces of equipment, "Working at full pelt, trying to cool down..." He stood up straight again. "Uh, wherever it is we are. Well, if ya can't stand the heat..." He walked towards a heavy-duty door, opened it and the trio walked through into a corridor that was somewhat cooler. "Well, that's better." the Doctor said.

"Oi, you three!" a voice called, and the trio turned to see three people sprinting towards them. One was a woman while the other two were men. All three looked rather grubby and sweaty.

"Get out of there!" the woman hollered.

"Seal that door, now!" the older-looking of the two men ordered the younger one, who slammed the door shut and locked it.

"Who are you? What're you doing on my ship?" the woman asked the three time travellers.

"Are you police?" the young man asked.

"Why would we be police?" the Doctor questioned.

"We got ya distress signal." Martha explained.

"If this is a ship, how come we can't hear the engines?" the Artist frowned.

"It went dead four minutes ago." the woman replied.

"So maybe we should stop chatted and get to engineering. Captain." the older man said irritably.

"Secure closure active." a computer voice announced.

"What?!" the woman stared.

"The ship's gone mad." the older man breathed.

A young woman came running up the corridor, doors slamming shut behind her. "Who activated secure closure?" she panted, "I nearly got locked into area 27." Then she noticed the three time travellers. "Who are you?"

"He's the Doctor, she's the Artist and I'm Martha. Hello." Martha replied, somewhat distracted by something out of the nearby viewport.

"Impact projection: 42 minutes. 27 seconds." the computer announced.

"We'll get out of this, I promise." the Captain reassured her crew.

"Doctor, Artist..." Martha said shakily, looking out of the viewport in horror at something outside.

The Artist went over to join Martha, while the Doctor turned to the Captain. "42 minutes till what?" he asked.

"Doctor, you need to look at this." the Artist said worriedly, so the Doctor joined the two women at the viewport and his eyes widened in horror at the sight outside.

They were aboard a ship that was hurtling towards a burning sun.

"42 minutes until we crash into the sun." the Captain said grimly.

The Doctor turned away from the viewport and raced back over to the Captain. "How many crew members on board?" he asked urgently.

"Seven, including us." she replied.

"We transport cargo across the galaxy." the older man explained, "Everything's automated. We just keep the ship..."

"Call the others, we'll get ya out!" the Doctor interrupted, dashing back towards the door where he'd came from.

"Doctor, don't!" the Captain warned as the Doctor began to open the door, but it was too late.

The Doctor pulled the door open and was immediately knocked off his feet by an intense blast of hot air. The young woman donned a heat visor and shut the door while the Artist and Martha helped the Doctor up. "But our ship's in there!" he said to the crew.

"In the vent chamber?" the young man asked incredulously.

"It's our lifeboat." the Doctor told him.

"It's lava." the older man said grimly.

The young woman removed her visor and checked a gauge. "The temperature's going mad in there!" she reported, "Up 3,000 degrees in 10 seconds and still rising."

"Channelling the air." the young man nodded, "The closer we get to the sun, the hotter that room's gonna get."

"Well, our ship can withstand those temperatures, but we can't." the Artist said, "So we'll have to find another way."

The Doctor quickly pondered the problem. "Right, we fix the engines, we steer the ship away from the sun. Simple!" he said, "Engineering down here, is it?" he asked the Captain as he took the Artist's hand and they ran off down a corridor.

————————————————————————————

"Impact in 40:26." the computer announced as the group arrived in the engine room.

"Blimey! D'ya always leave things in such a mess?" the Doctor remarked, taking a look around the room.

"Oh, my god!" the Captain gasped.

"What the hell happened?!" the older man breathed as they all walked over to a completely wrecked engine. Wires, springs and pieces of casing were scattered all over the place, all steaming. It was such a shambles, that the TARDIS console room looked spotless in comparison.

"Oh, it's wrecked." the young man groaned, surveying the totalled engines.

"And it's not an accident." the Artist said grimly, "Whoever did this knew exactly what they were doing."

"Where's Korwin?" the Captain wandered, looking around, "Has anyone heard from him or Ashton?"

"No." the older man shook his head.

"D'ya mean someone did this purpose?" Martha asked the Artist, who nodded grimly.

The Captain ran over to an intercom on the wall. "Korwin? Ashton? Where are you?" she asked, receiving no response, "Korwin, can you answer?" Still no answer. "Where the hell is he?" the Captain wandered, "He should be up here!"

The Doctor meanwhile was fiddling about with a computer screen that was still functioning. "Oh, we're in the Torajji system, lovely!" he remarked, "Ya a long way from home, Martha. Half a universe away."

"Yeah, feels like it." Martha replied sarcastically.

The Doctor turned to the Captain. "And ya still using energy scoops for fusion?" he asked, "Hasn't that been outlawed yet?"

"We're due to upgrade next docking." the Captain replied dismissively, though both Time Lords saw her and the young man exchange guilty looks. Clearly, they were trying to cut corners to save money. "Scannell, engine report." the Captain called to the older man.

Scannell walked over to the computer terminal the Doctor was at before and performed a scan. "No response." he said grimly and ran over to the wrecked engine.

"What?!" the Captain stared.

"They're burnt out." Scannell replied, he and the Artist examining the wires protruding from the wreckage, "The controls are wrecked. I can't get them back online."

"I'm afraid this lot's wrecked beyond hope." the Artist concurred, "But I trust you have auxiliary engines?"

"Yeah, but we don't have access from here." the Captain replied, "The auxiliary controls are in front of the ship."

"With 29 password-sealed doors between us and them." Scannell added gloomily, "We'll never get there in time."

"Can't you override the doors?" Martha suggested.

"No. Sealed closure means what it says." Scannell told her, "They're all deadlock sealed."

"So, a couple of sonic screwdrivers're no use." the Doctor muttered.

"Nothing's any use." Scannell said defeatedly, "We've got no engines, no time, and no chance."

"Oh, listen to you! Defeated before you've even started!" the Doctor remarked, "Where's ya Dunkirk spirit?!" He turned to the Captain. "Who's got the door passwords?"

"They're randomly generated." the young man interrupted, "Reckon I know most of 'em. Sorry, Riley Vashti." he introduced himself.

"Then what're ya waiting for, Riley Vashti? Get on it." the Doctor ordered, taking charge.

"Well, it's a two-person job." Riley replied, grabbing a huge magnetic clamp off the wall behind him and a backpack too, "One to answer the questions, the other to carry this." He put the kit on his back. "The oldest and cheapest security system around, eh Captain?"

"Reliable and simple, just like you, eh Riley?" the Captain retorted.

"Try and be helpful, get abuse. Nice!" Riley joked.

"I'll help you." Martha said, taking some equipment from Riley, "Make myself useful."

"It's remotely controlled by the computer panel. That's why it needs two." Riley explained, then turned and headed away from the group.

"Be careful, Martha." the Artist warned her friend.

"You too." Martha smiled, then turned and followed Riley away.

Just then, a male voice came over the intercom; "McDonnell, it's Ashton."

The Captain, Kath McDonnell, ran back over to the intercom panel. "Where are you? Is Korwin with you?"

"Get up the med-centre now!" Ashton urged, sounding deadly serious. So McDonnel left the intercom panel and ran off, the Doctor and the Artist following her.

"Impact in 34:31." the computer announced.

————————————————————————————

In the med-centre, a man, Korwin, was thrashing about in agony on a bed next to a stasis chamber, his eyes shut tight. A balding man, Ashton, and a black women in medical scrubs, Abi, were trying to restrain him. "You've gotta stop it!" Korwin screeched.

"Korwin, it's Abi. Open ya eyes, I need to take a look at you!" Abi encouraged.

"Korwin!" McDonnell cried as she came running in, "What's happened?! Is he okay?"

"Kath, help me!" Korwin wailed, "It's burning me!"

"How long's he been like this?" the Artist asked as she and the Doctor approached the foot of the bed.

"Ashton just brought him in." Abi replied.

The Doctor took his sonic out and began to scan Korwin. "What're you doing?!" McDonnell demanded

"Sonic impulse." the Doctor waved her off.

"Don't get too close." Ashton warned.

"Don't be so stupid, that's my husband!" McDonnel glared at him.

"And he's just sabotaged our ship!" Ashton retorted.

"What?!"

"He went mad. He set the ship to secure closure, then he set the heat pulse to melt the controls."

"No way! He wouldn't do that!" McDonnel protested.

"I saw it happen, Captain." Ashton told her.

The Doctor finished his scan of Korwin and tried to talk to him; "Korwin? Korwin, open ya eyes for me a second."

"I can't!" Korwin wailed.

"Of course you can." the Artist encouraged, "Go on."

"Don't make me look at you! Please!" Korwin begged.

"Alright, alright, alright. Just relax." the Doctor said, picking up a hypo-gun off a tray. "Sedative?" he asked Abi.

"Yes." Abi nodded, and the Doctor pressed the gun against Korwin's neck and administered the sedative. Korwin gave one final shout, then fell silent and still.

"What's wrong with him?" McDonnell asked.

"Rising body temperature, unusual energy readings..." the Doctor replied, perching on the bed and crossing his arms, "Stasis chamber. I do love a good stasis chamber. Keep him sedated in there." he instructed Abi, "Regulate the body temperature." Abi looked at him questioningly, but did what he said anyway. "And just for fun, run a bio-scan and tissue profile on a metabolic detail."

"Just doing them now." Abi replied, working on a scanner.

"Good work." the Artist praised, "Has anyone else been showing these symptoms?"

"Not so far." Abi replied.

"Well, that's something." the Doctor muttered thoughtfully.

"Will someone tell me what is the matter with him?!" McDonnell demanded.

"Some sorta infection." the Doctor replied, "We'll know more after the test results. Now, allons-y, back downstairs, eh? See about those engines. Go."

Ashton made to leave but McDonnell stayed out, unwilling to leave her husband. "Come on, Captain." the Artist encouraged, "This ship needs it's captain in this emergency."

So McDonnell reluctantly left. "Call us if there's news." the Doctor called to Abi as he and the Artist made to follow, "Any questions?"

"Yeah, who are ya?" Abi scoffed.

"I'm the Doctor." the Time Lord replied simply, then he and the Artist hurried off after McDonnell and Ashton, leaving Abi alone in the med-centre. She turned to run some more tests, not noticing Korwin's hand twitch.

"Heat shields failing." the computer announced, "At 25%. Impact in 32:50."

————————————————————————————

Martha and Riley reached the first locked door and Riley began typing into a keypad. "Hurry up, will you?" Martha urged him.

"Alight." Riley replied, finishing his typing, "Fix the clamp on."

Martha lifted the clamp up and attached it to the door, holding it there, then turned to see Riley typing again. "What're you typing?" she asked him.

"Each door's trip code is the answer to a random question set by the crew." Riley explained, "Nine tours back, we got drunk, thought 'em up. Reckoning was if we're hijacked, we're the only ones who know all the answers."

"So you type in the right answer..."

"Sends an unlock impulse to the clamp." Riley confirmed, "But we get only one chance per door. Get it wrong, the whole system freezes."

"Better not get it wrong, then." Martha muttered.

"Okay.." Riley said to himself and shifted over to a readout screen, where the first question had appeared. "'Date of SS. Pentallian's first flight?' That's alright!" He typed in the answer to the question. "Go!" he yelled to Martha.

Martha pressed a button on the clamp and the lights on top of it turned green and the door opened. "Yes!" Martha cheered.

"Only 28 more to go." Riley said, running for the door.

————————————————————————————

The Time Lords were back in the engine room. The Artist was trying to fix the wiring while the Doctor went over to the intercom panel. "Abi, how's Korwin doing?" he asked, "Any results from the bio-scan?"

"He's under heavy sedation." Abi replied, "I'm just trying to make sense of this data. Give me a couple of minutes and I'll let ya know."

"Martha, Riley, 'ow ya doing?" the Doctor asked.

"Area 29, at the door to 28." Martha replied.

The Doctor checked a read-out above the panel. "You've gotta move faster!" he urged.

"We're doing our best!" Martha retorted.

"'Find the next number in the sequence: 313, 331, 367...' What?" Riley's voice said.

"You said the crew knew ALL the answers."  Martha reminded him.

"The crew's changed since we set the questions."

"You're joking..."

"379!" the Doctor told them.

"What?"

"It's a sequence of happy primes. 379."

"Happy what?"

"Just type it in!" the Doctor hollered.

"Are yer sure? We only get ONE chance!" Riley pointed out.

"Any number which reduces to one when ya take the sum of the square of it's digits and you continue iterating until it yields is a happy number." the Doctor told them at his trademark 100mph, "Any number that doesn't, isn't. A happy prime is a number which is both happy and prime, now type it in!" He turned to the Artist. "I dunno, talk about dumbing down! Doesn't anyone teach recreational mathematics any more?"

"Oi, not everyone can be an all-knowing genius like you." the Artist retorted.

"You're a genius too." the Doctor told her. The Artist was always so modest and humble that she sometimes didn't know just how clever she actually was.

"We're through!" Martha said over the intercom.

"Keep moving, fast as ya can." the Doctor urged, "And, Martha, be careful. There may be something else on board this ship."

"Anytime you wanna unnerve me, feel free!" Martha groaned.

"Will do, thanks." the Doctor replied cheekily and went back to help the Artist.

"That thing that infected Korwin?" she asked him. He nodded. He didn't know what had infected Korwin, but he had a bad feeling that it couldn't be good.

"Impact in 30:50." the computer droned on.

————————————————————————————

Martha and Riley reached the next door. "I can't believe our lives depend on some stupid pub quiz!" Martha grumbled, "Is that the next one?"

Riley put his head in his hands. "Oh, this is a nightmare!" he groaned, sounding downtrodden, "'Classical music. Who had the most pre-download number ones: Elvis Presley or The Beatles?' How're we supposed to know that?"

————————————————————————————

The Doctor surveyed a wrecked piece of equipment. "We need a backup in case they don't reach the auxiliary engines in time." he decided, "Come on, think! Resources, what have we got?!"

Martha's voice came over the intercom; "Doctor?"

"What is it now?"

"Who had the most number ones: Elvis or The Beatles? That's pre-download."

"Elvis!" the Doctor answered confidently, only to second guess himself. "No! The Beatles! No! Wait! Um... um..." He slapped the back of his head, trying to rack his brains. "Argh! What was that remix? Oh, I dunno. Do you know?" he asked the Artist.

"Afraid not." she shook her head, "I'm more of a 80's rock girl myself."

"Martha, we don't know. We are a bit busy!" the Doctor said into the intercom.

"Fine. I'll ask someone else." a put-out Martha retorted.

"There was no need for that." the Artist scolded the Doctor for his rudeness, then turned to the crew. "This ship's still got power, so that means the generators are still going. If we could harness that..."

"Use the generators to jump-start the ship!" McDonnell realised.

"Exactly!" the Doctor grinned, proud of the Artist for coming up with that idea, "At the very least, it'll buy us more time."

"That... is brilliant." McDonnell praised.

"See, told ya you were a genius too." the Doctor said to the Artist, who just blushed modestly.

"If it works." Scannell said pessimistically.

"Oh, believe me, you're gonna make it work." McDonnell told him, and Scannell went off to do as he was told.

"He's a cheery one, isn't he?" the Artist remarked, then she and Ashton went off to help Scannell.

"Impact in 29:46." the computer announced.

————————————————————————————

Seeing that the Time Lords were to be of no help, Martha decided to try her mother. She dialled Francine's number and to her surprise, she answered; "Hello?"

"Mum? It's me, it's Martha. Wow!"

"Where are you?" Francine demanded, "Don't you check your messages? I've been calling you."

"Actually, bit busy." Martha cut her off, not having the time to listen to her mother's trademark ranting and moaning in this emergency, "Need you to do something for me."

"No. Listen to me. We have to talk about this Doctor and that Artist