"So," said Martha. She was jogging along the familiar corridors of the Royal hope before the tall figure of the doctor and beside the very blonde Rose Tyler. "Why exactly were you admitted into hospital?"

"Well I was admitted for abdominal pains," she said carefully. "But really I don't need hospital treatment."

"Oh?"

"Actually me and the Doctor are sort of… investigating something. The Doctor noticed something or other about this place, some kind of signal, didn't you love?"

"Mmm," he said, striding ahead of the two young women. "Plasma coils."

"Plasma coils?" said Martha. "I've heard that before…"

"You have?" asked Rose, surprised. "Well, I guess you're a doctor…"

"No, not from med school," laughed Martha. "I used to date this guy, Terry his name was, and he was a proper geek for all that clever physics stuff. My sister used to tease me about him like hell."

"When did you break up?" Rose asked curiously. She always had been one for gossip- even if they were stranded on the moon. And she hoped beyond hope that this 'Terry' and this 'Martha' still had loose ends to tie. That way it would keep the bitch away from her husband.

"Three years ago," said Martha, dashing Rose's hopes with that single utterance. "I haven't actually had a relationship since then. I've been too busy with my studies."

"Three years?" said Rose, her eyes wide. "Does that mean no sex for three years?"

"I didn't say that," said Martha. "I mean… no serious relationships. And I get a little reckless when I've had too much to drink. Good girl gone bad scenario. It's quite embarrassing. My sister blackmails me by threatening to tell my mother. Not very often at all… but once in a while." Rose smirked.

"Badass." In her head she added, slut.

"No sex for three years," smirked the Doctor. "Rose Tyler. One track mind."

"Only you, sweetie," she smiled. She turned back to Martha.

"So are you a doctor then? Or a nurse? Or a… whatever else."

"I'm a med student," she said. "Nearly a doctor. When I pass my exams."

"I haven't had an exam since my GCSE's," said Rose. Martha smiled tiredly.

"I have."

"And here we are," announced the Doctor. He smiled vaguely at the two women behind him. "Ready?" Martha nodded, a lump rising in her throat.

"Yes," she said. Her pulse was quickening as the Doctor tried the handle of the door and slowly pushed it open… The three people sucked in a deep breath and looked at each other for confirmation. They could breathe. Martha stepped out onto the balcony. "We have air," she said softly. "How does that work?"

"Just be glad it does," replied the Doctor as he rested his hands on the crude block of stone that provided the railings at the end of the balcony. Rose was looking around in wonder.

"The moon," she said. "All those places we've been yet we've never been to the moon. I guess, compared to everything else, it seemed so boring. But it's not…" her voice trailed off. Martha sighed, staring down at the earth, imagining the pandemonium down there caused by the sudden vanishing act of the Royal Hope. She imagined Tish, who she had been speaking to seconds before it happened. Leo- 21 today maybe hearing about it on the news or from their big sister. Her parents. Would they be crying?

"I've got a party tonight," she heard herself say. Both the Doctor and Rose's heads turned to look at her. "My brother's twenty-first. Oh my God my mother's gonna be…" And for a second she could cry. She forced the tears down. She was being stupid, crying would solve nothing.

"Are you ok?"

"Yeah," she said.

"Sure?"

"Yes!" she said, with more force this time. She took a deep breath and composed herself. Rose moved forward to the balcony.

"D'you want to go back in?" asked the Doctor.

"No way," said Martha. "I mean we could die any minute but all the same…"

"It's beautiful," said Rose. The Doctor looked at the two star struck- or moon struck- women.

"You think?"

"I mean how many people wanted to go to the moon? And here we are!"

"Standing in the earthlight." There was a moment's silence. Then Martha spoke again.

"What do you think happened?"

"What do you think?" asked the Doctor. He was testing her, Rose realised. Testing if her intellect lived up to her shown bravery. And looks. There was something about this Martha Jones, something that made Rose want to hold onto the Doctor and protect him from the young med student. She was certainly more intelligent than her, Rose realised, and she was also extremely good looking. And she and the Doctor seemed to be getting on pretty well- too well for Rose's liking. She half hoped that Martha would get the question wrong.

Martha looked at them both; as if she worried her answer might cause offence. "Extra-terrestrial," she said in a rush. "It's got to be. I know it have sounded mad a few years ago but these days? That spaceship flying into Big Ben, Christmas- that thing in the sky those cyber men things…" Rose looked across at the Doctor. This girl was good. "I had a cousin," said Martha. "Adeoli. She worked at Canary Wharf. Never came home." The Doctor's head jerked.

"I'm sorry," he said.

"Yeah."

"I was there," he said dreamily. "We were there. In the battle. It was…"

"My whole family," said Rose. "I put them in so much danger. It was… well it ended well."

"You were there?" asked Martha curiously. "Did you… meet my cousin? Adeoli. Did you see her?"

"Yes," he admitted. "Briefly. Yes." Martha nodded, and turned back to look at the earth.

"Well," she said. "We'll find a way out. If we can travel to the moon then we can travel back. There's got to be a way."

"Right," said the Doctor. "Better start finding out the way then. Let's have a look there must be some kind of-" He picked a small object of the ground and before Martha could open her mouth to speak he hurled it into the air. It bounced off something, something that rippled blue. "Force field," he finished.

"Keeping the air in," said Rose. Martha nodded.

"So if we're in this big bubble," she said slowly. "That's all the air we've got. What happens when it runs out?" The Doctor replied with another question.

"How many people in this hospital?"

"I dunno, about a thousand?" The Doctor stared back at the building a misty look in his dark brown eyes.

"A thousand people," he said. "Suffocating." Martha was appalled.

"Why would anyone do that?" The Doctor wasn't looking at her, or Rose.

"Ask them yourselves." He was looking up towards the sky. "Heads up!" Both Rose and Martha spun round and watched, hearts in their mouths. Something big, black and dark was descending from the sky. It was like a tube, a massive tube that stayed upright-there was no need to be aerodynamic- studded with levels and lights. Martha grabbed hold of the Doctor's arm almost by instinct and Rose was disgusted that he didn't shake it off. She barged over and wrapped the Doctor into a tight hug, making sure that Martha's hand was jolted off his wrist. Martha stepped back a little, surprised, but not half as surprised as the Doctor himself. He patted the women's back awkwardly.

"Rose," he said. "Slight problem, thousands of humans suffocating, Judoon descending onto the surface of the moon… never waste time in a hug…"

"Sorry," she said jumping back and flicking her blonde hair back. "I just wanted to hug you. We are married, of course. In love. You know. Just in case anyone was thinking of butting in or anything. Not that they were, of course. Nobody would ever dare do that." At this point she looked sharply at Martha. The Doctor stayed oblivious to her tone and twisted round to look back at the ships.

They had landed now, in a blur of moon dust, and something was moving. Small figures were marching, marching like soldiers, from the black tubes. Martha strained her eyes to look, excitement fluttering in her chest.

"That's aliens," she said. "Real, proper aliens!"

"Judoon," said Rose. Martha leaned over the balcony to watch as they paraded forward, a column of storm troopers in heavy black armour and clutching lethal looking guns.

"They have rhino heads," she gasped. "Aliens with rhino heads! This is brilliant!"

"No it's not," said the Doctor. "Martha, Rose, with me. If the Judoon are here, things can't be good." He led the way off of the balcony followed by Rose. Martha took one quick glance back at the astonishing surface of the moon and followed the husband and wife.

As Martha swung the door closed behind the body of Mr Stoker, senior consultant, dropped to the floor, completely drained of blood.

The Doctor led the two women (who were now glowering at each other, all of Rose's previous friendly nature gone) to the hospital foyer. They stopped just before the stairwell and crouched on the floor, staring through the tinted glass at the scene down below. People, doctors and patients alike, were gathered in small little hysterical groups, huddled on the floor. The doctor within Martha longed to go down and help them- but the sight of the oncoming Judoon kept her where she was. The first of the rhino headed aliens barged through the doors, holding their guns aloft. The people shrank away, screaming in disgust. Martha swallowed as she recognised her archenemy Miranda (the bitchiest med student on the planet) and Ralph, the man with the broken knee that the Doctor had been talking to earlier cowering from the aliens.

"Bo!" The Judoon was talking in a crude alien language. Martha shivered. "Sco! Fo! Do! No! Kro! Blo! Co! Sho! Ro!' All the aliens raised their weapons. A bloke in a white coat identical to Martha's slowly walked forwards. James Morgenstern- another trainee doctor and a bit of a geek. He opened his mouth to speak.

"Um… we are citizens of planet earth… we welcome you in peace-" The Judoon leader strides forward and slammed the young man against the wall. He gasped, to scared to do anything else. Martha craned her neck forward. Please let him be okay… The Judoon shoved a torch thing was a blue light in his face and slowly trained it up and down his body.

"What's he doing?" hissed Martha. "What's he doing?"

"Brave boy," said Rose slowly. "Who is he?" Martha didn't answer; she could hear Morgenstern talking again.

"I'm sorry please don't hurt me I was only trying to help I'm sorry please don't hurt me…" he stuttered. Martha bit her lip.

The Judoon took back his strange blue device and pressed a button. Then, issuing from the torch thing, came Morgenstern's panicked stutter.

"I'm sorry please don't hurt me I was only trying to help I'm sorry please don't hurt me…"

The Judoon grunted and inserted the device into the front of his armour. Then a look of understanding came on the twisted hide of his face and he spoke in voice that was- no matter how gruff and twisted- clear English.

"Language assimilated. Language: earth English. You will be catalogued." He then thrust a second device into Morgenstern's face, another small, handhold torch. "Human." He flipped the device around and marked his hand with a cross. Morgenstern looked at his hand in bewilderment, but the alien seemed to be done with him, letting him fall free and turning to his troops. "Catalogue all suspects."

"Doctor," said Martha. "What's going on?"

"Look down there, you've got a little shop. I like a little shop," he replied.

"Never mind that, what are the judoon?"

"They're police. Well, police for hire, more like interplanetary thugs."

"And they brought up to the moon?" Martha asked. She wondered how the Doctor knew all this. What was he?

"Neutral territory. According to Galactic law, they've got no jurisdiction over the Earth. So they isolated us. The rain, the lightening, that was them, using an H20 scoop." Rose looked across at Martha to see her answer.

"What are you on about, galactic law, where d'you get that from?" He raised his eyebrows and shifted his position to get a better view. She sighed and followed him. "If they're police, are we under arrest? Are we 'trespassing on the moon' or something?"

"No but I like that! Good thinking!"

"I was about to say that," said Rose.

"Yes," said the Doctor impatiently. "Anyway, Martha, I wish it was that simple. If they're making a catalogue, that means they're after something non-human which is bad news for me?"

"Why?" He just looked at her. She raised her eyebrows. "Oh don't be ridiculous." She looked at Rose who was staring at her defiantly. Back at the Doctor. "Don't be ridiculous… stop looking at me like that!" He smiled.

"Come on then." He headed back towards the stairs. Rose followed him, making a big show of entwining her arm around his and pecking him on the cheek. Damn him! Martha sighed, and got up to follow him.

III

They were crouched down low when the Judoon pounded past them, up on the sixth floor. People were screaming, genuine fear and terror struck against their sickly faces as they tried to run.

"Prepare to be catalogued!" Morgenstern ran past the Judoon.

"Do what they say- all they want to do is shine this light thing it's not going to hurt us just listen to them!" Martha watched as a man picked up the nearest chair and swung it at the nearest Judoon. Martha's heart leapt- she recognised that patient. He was on her rounds last week- some kind of heart problem she recalled. She remembered seeing his wife and daughter come to visit him just yesterday, the child of three, handing him a get well card…

"Charge. Physical assault. Plea. Guilty. Punishment. Execution." A vicious red beam blasted out of a large gun and the man was completely incinerated. The Judoon thundered past, cataloguing people, until they slowly filtered out of the floor- then The Doctor, Rose and Martha leapt from their hiding place and began to sprint down the corridors.

III

Rose sat on the desk of the nurse's station as the Doctor scanned the computer with his sonic. Martha had gone to look round the hospital in an attempt to track the Judoon's progress.

"What are you doing?" Rose asked, swinging her legs in the thin air.

"Uh… looking for anything unusual," he said, his brow furrowed in concentration.

"Right," she said. There was a pause. "What do you think about this 'Martha' then?" she asked slyly.

"Martha? Seems…" he hesitated, unsure of what to say. "Great. Really great."

"Great?" she said. "Because she's a doctor?"

"Rose, how many doctor's are there in this place?" he asked irritably. "I like Martha because… I do. End of. Why should it bother you?"

"Doesn't she annoy you?" Rose asked, playing with his hair. He flicked her hand away. She sighed. "Why won't she leave us alone?"

"Because I don't want her to," he said. "Now can you stop talking Rose I'm trying to think."

"Oh," she said, flicking her blonde hair behind her. "So now 'Martha's' here you won't be listening to me anymore? You won't need me, huh? Well if that's how it is, I might as well go now!"

"Rose, we're stranded on the moon, there aren't all that many places to go to," he said. "Anyway, now Martha's here, nothing has changed. I'm just busy." Martha burst in the room.

"They've reached the third floor- oh sorry. Were you fighting?"

"No," said the Doctor easily. "Rose just seemed to think you were replacing her." Rose opened her mouth.

"I did not say that!" she said. Martha put a hand on her hip.

"What were you saying, then?"

"I was saying… why should it matter to you anyway?" she cried angrily. Martha stepped forward.

"What's that?"

"A sonic screwdriver, are you stupid?" shouted Rose.

"Rose!"

"It's ok," said Martha. "So what is it?"

"A sonic screwdriver."

"Well if you're not going to answer me properly-"

"No it is! It's a screwdriver and it's sonic."

"What else have you got? Laser spanner?"

"I did but-"

"It was stolen by Emily Pankhurst," said Rose. "I was there." Martha frowned and the Doctor rattled the computer.

"What's wrong with this computer?" he growled. "The judoon must of locked it- a judoon platoon upon the moon. Cos I swear I was just travelling I swear, I was just wondering I, wasn't looking for trouble, honestly I wasn't. But I noticed these plasma coils around the hospital- like, that lightning, that's a plasma coil it's been building up for two days now- so I checked in. I thought something was going on inside. Turns out the plasma coils were the Judoon up above.

"What did you say they were looking for?" asked Rose.

"Something that looks human but isn't."

"Like you," pointed out Martha. "Apparently."

"Like me, but not me."

"Haven't they got a photo?"

"It could be a shape changer."

"Well whatever it is, can't you just leave the Judoon to find it?"

"If they find the hospital guilty of harbouring a fugitive… they'll sentence it to execution?"

"All of them?" said Rose.

"All of us," said Martha. "You're here now."

"All of us," said the Doctor. "But if I can find it first… Oh D'YOU SEE! They're thick, Judoon are thick, they wiped the record- oh that's clever."

"What are we looking for?" Martha asked.

"I don't know, any patient admitted in the last week admitted with unusual symptoms."

"You keep looking, I'll go and ask Mr Stoker he might now," she said.

"Be careful!" he called.

"Gotcha." She smiled and left the room, hesitating by the door just long enough to hear Rose utter:

"What a little bitch."