"Heat shields failing," the computer voice reached Rose's ears. "At twenty-five percent. Impact in thirty-two fifty."

Rose turned to look at Riley. The man was typing various codes into the lock machine looking at the screen intently. Rose was holding the magnetic clamp waiting for Riley's signal to attach it to the bulkhead. Currently they were still at Area 29, just a floor down from the med-centre.

"Hurry up, will you?" Rose groaned adjusting the clamp in her hands.

"Alright," Riley nodded. "Fix the clamp on!"

Rose pushed the clamp against the bulkhead with a grunt and it locked in place. Riley went back to the lock machine and began typing in various words again.

"What are you typing?" Rose asked him, craning her neck over her shoulder to look at him properly.

"Each door's trip code is the answer to a random question set by the crew," Riley said. "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," Rose tried to grasp what he was saying.

"This," Riley patted the box screen in front of him. "sends and unlock pulse to the clamp. But we only get one chance per door. Get it wrong, the whole system freezes."

"Better not get it wrong then," Rose smirked.

"Okay!" Riley smiled as the first question appeared on the screen. "Date of SS Pentallian's first flight?" He read the question to Rose. He smiled and typed a word into the box. "That's alright! Go!"

Riley pointed to Rose just as the clamp let out a beep. A green light flashed on the machine and the door opened before her.

"Yes!" Rose looked back and smiled at Riley.

"Twenty-eight more to go!" Riley grinned and laughing happily as the two ran down the corridor.

⋆⋆⋆DW⋆⋆⋆

"Rose, Riley? How're you doing?" the Doctor's voice came through the speakers.

"Area 29 at the door 28," Rose called as she ran over to the bulkhead. Both she and Riley were panting hard from running, sweat dripping down from their foreheads.

"Yeah, you've got to move faster!" the Doctor said.

"We're doing our best!" Rose said rather annoyed. The lock machine chirped behind her and Riley read the next question.

"Find the next number in the sequence: 313, 331, 367, …?" Riley furrowed he brow and looked at Rose. "What?"

"You said the crew knew all the answers," Rose reminded him.

"The crew's changed since we've set the questions," Riley muttered.

"You're joking."

"379!" the Doctor's voice yelled through the intercom.

"What?" Rose asked.

"It's a sequence of happy primes, 379!"

"Happy what?" Rose shot a confused look to Riley. The man shrugged back.

"Just enter it!" the Doctor called.

"Are you sure?" Riley looked to speaker on the ceiling. "We only get one chance."

"Any number that reduces to one when you take the sum of the square of its digits and you continue iterating until it yields one is a happy number. Any number that doesn't isn't. A happy prime is a number that is both happy and prime," the Doctor ranted. "Now type it in! I don't know, talk about dumbing down! Don't they teach recreational mathematics anymore?"

Riley blinked and stood still for a moment. Then, with a shake, he jumped back over to the question machine and typed in the number. Rose felt the clamp give way and portal 28 opened.

"We're through!" she called to the Doctor.

"Keep moving, fast as you can," the Doctor said. "And Rose, be careful. There may be something else aboard this ship."

"Anytime you want to unnerve me, feel free," Rose muttered sarcastically.

"Will do, thanks," the Doctor said in a cheery tone.

"Impact in thirty fifty," the computer droned.

⋆⋆⋆DW⋆⋆⋆

"I can't believe our lives depend on some stupid pub quiz," Rose sighed when they reached Area 27. "Is that the next one?"

Another question had appeared on the screen. Rose stared in disbelief as she read it.

"Oh this is a nightmare," Riley breathed. "Classical Music: Who had more pre-download Number Ones, Elvis Pre-sley or the Be-atles?"

Riley turned to Rose with a shocked expression and shook his head.

"How are we supposed to know that?"

Rose turned and gave him a knowing smile. Reaching forward she turned the intercom on, and the Doctor's voice came through.

"We need a backup in case they don't reach the auxiliary engines in time," he was saying. "Come on, think! Resources! What have we got?"

"Doctor?" Rose interrupted his conversation with the crew.

"What is it now?" he said with an irritated tone.

"Who had the most Number Ones, Elvis or the Beatles?" Rose read him the question. "That's pre-download."

"Elvis," he said first. "No! The Beatles! No, wait! Um, um, oh, what was that remix? Er, I don't know! I am a bit busy!"

"Fine," Rose said. "I'll ask someone else."

⋆⋆⋆DW⋆⋆⋆

"Now, where was I?" the Doctor said back in the engine room. "'Here comes the sun.' No, resources! So, the power's still working, the generator's going. If we can harness that, ah!"

"Use the generator to jumpstart the ship," McDonnell's nodded.

"Exactly!" the Doctor grinned. "At the very least, it'll buy us some more time."

"That," the Captain raised her brows at him, "is brilliant,"

"I know, see?" the Doctor looked to Scannell and the mechanic that had now been introduced as Erina. "Tiny glimmer of hope."

"If it works," Scannell said.

"Oh, believe me," McDonnell turned to the pessimist. "You're gonna make it work."

Scannell scowled at them and turned away. Ashton let out a snort of laughter and the Doctor ginned.

"That told him!" the Doctor smiled.

"Impact in twenty-nine forty-six."

⋆⋆⋆DW⋆⋆⋆

Rose paced the corridor with her phone in hand, waiting for Jackie to pick up. Riley watched her dubiously, not thinking she could reach anybody out here in deep space.

"Hello?" Jackie's voice called out.

"Mum, it's me! It's Rose!"

"Rose! Oh, my sweet girl!" Jackie squealed. "Where are you? It's been like three months since you last called! Don't you even think about filling your own mother in on your travels with that man? How's the Doctor anyway? Is he there? Hello, Doctor! Are you taking care of my daughter? When are you—?"

"Mum, he's not here right now," Rose cut her off. "Actually, a bit busy. Need you to do something for me."

"What?" Jackie shouted. "Three months and not a word, and all you called me up for is for me to do you a favor? I don't think so, young lady! Now, you tell me what you two are up to. Be quick about it!"

"Mum, please, not now!" Rose said exasperatedly. "I need you to look something up on the internet."

"Do it yourself," Jackie snapped. "You've got a computer on the TARDIS."

"Oh, just do it, will you?!" Rose shouted, hearing her voice echo in the corridor. Turning slowly, she saw Riley staring at her with raised brows. She gave a small smile and turned away, her cheeks getting red.

"Please," Rose said into the phone.

"When did you get so rude?" Jackie said. "I'll tell you when. Ever since you met that man!"

Rose rolled her eyes at Riley. He smiled and rubbed the sweat from his brow.

"I need to know who had more Number Ones," Rose nodded. "The Beatles or Elvis?"

"Hang on, the mouse is unplugged," Jackie muttered. Rose leaned her head back and let out a groan, pacing back and forth impatiently.

"Okay, I'm on it," Jackie said. "What is this, a pop quiz?"

"Yeah," Rose said quickly. "A pop quiz!"

"Using your mobile is cheating," Jackie scolded.

"Have you found it?"

"There's over four-hundred thousand results," Jackie said. "Give me a minute!"

Rose looked up at the metal ceiling angrily. She flinched as the computer came over the intercom again.

"Impact in twenty-eight fifty."