Author's Notes:
Written for 2008 dw_femslash

"Project Indigo, this is Martha Jones, reporting that test jump number four is a go. Not that you'll hear this, because for some reason we can't establish a communications link between the jump point and base. But if we could, I'd be able to tell you guys that this cave still smells like mouldy bread." Martha switched off the recorder, flipped open the GPS transmitter and sent the requisite burst of signal, though she knew it wouldn't make contact. The analysts hadn't told her if this was because the cave was too far underground to reach the satellite or due to the Indigo device's habit of interfering with local electrical signals. Now that the dust had settled after the most recent Dalek invasion, UNIT were taking their time with Project Indigo. Martha believed in being methodical, but in the back of her mind, she wondered if they were punishing her for using the Indigo device during the invasion. The mere fact that she was alive was proof of her hasty and unsanctioned actions, and it hardly helped to claim that her deceased superior had given her an order. Martha knew the device worked and she was getting tired of seeing the same old cave, but it had been hard enough to convince UNIT to let her teleport to an unknown location, and she didn't want to press her luck again.

The cave was also dark - and for the fourth time in this test series, Martha took three steps off the jump site and walked straight into a low-hanging stalactite, cracking her forehead hard against the crumbly rock. Every time, she forgot to duck.

"Damn you!" Martha gave the spindly column a good shove with her shoulder and it snapped off at the top with a shower of rubble that clogged her nose and filled her eyes with grit. She coughed, then jumped as the timer attached to her belt exploded into a fury of beeps and vibrations. Martha scrubbed at her eyes in a vain attempt to clear them, but after four jumps she could find the right spot with her eyes closed. She moved three steps back, glad for the marker she had taped to the cave floor on the first jump. Once she was certain of her position she activated the teleporter.

Some moments after Martha had vanished, a voice called down from the newly opened hole in the roof. "Is there someone down there?"

***

The cave was still dark, still damp and still smelled like an old sandwich. Martha took a step off the teleport point, and walked straight into the stalactite. She put her hand onto it, confusion distracting her from the pain . "I broke this off!" The rock was crumbly in her hand, and it snapped easily, raining rock fragments down on her head. She blinked the dust out of her eyes - pale light was filtering down from a crack in the roof.

"Is there someone down there?" The voice came from the new opening in the rock wall. "If there's someone down there, I think it's only fair to warn you that I'm armed to the teeth."

Martha hesitated. The voice was pure London - and there was light. Maybe she was somewhere below the city? One of the tube stations? She moved around the opening, trying to find line of sight with the person on the other side. "Who's there? My name's Martha."

"Look out below!" More rock broke away, and Martha ducked away from the falling debris.

When the air cleared, a woman leaned on her stomach through the opening. "How'd you get down there?" She was young, round faced, and her bomber jacket puffed up as she hung comfortably upside down, half in and half out of the cave roof. "I'm Ace. Are you human?"

It was that last question that prickled at her imagination. "What else would I be?"

Ace opened her mouth to answer, but her voice was drowned out by the electronic cacophony of Martha's timer, and she pulled back with a wary expression. "What's that about, then?"

Martha switched it off, and started counting in her head - if she didn't make the jump within sixty seconds, Indigo would activate the return sequence automatically. "It's a reminder - I have to get back to base right now."

Ace looked up and down the length of the cave, dubiously. "And base is somewhere down there, is it?"

Martha looked over her shoulder at the jump point. If she backed up now, she wouldn't be able to keep talking to Ace. Did she really need to teleport from the same spot? Indigo had back-up programming to prevent her from teleporting into solid matter. "It's complicated — I'm sort of a test pilot. I have to go, right now, sorry. But just wait. I'll be back in a bit." She put her hand on the trigger, and activated the device. Air rushed into the place where she had been standing, kicking up chalky clouds of dust.

Ace coughed, swinging back and forth as she hung through the hole in the ceiling. "People come and go so quickly here!"

***

Martha talked the techs into extending the length of time she would remain at the jump site on the next test. Just to explore the boundaries of the cave, she told them, quashing her guilt at withholding information, but dreading the delays that such a discovery would entail. Instead, she won an extra hour with the promise of soil samples and air samples and water samples and any other samples that might help them identify the geographic position of the cave. They organised a second jump for the day and, an hour after she had left, Martha was teleporting back to find out more about a woman who needed to ask if someone is human.

The cave was dark again, but the ever-present smell of mildew told Martha she was in the right place. She stepped off the marker and reached for her torch, then the world exploded into a bright shower of red light behind her eyelids as her forehead made contact with the low-hanging rock formation. With an incoherent shriek of rage, she took to it with the torch, beating the limestone until the roof caved in around her.

"Is there someone down there? If there is someone down there, I think it's only fair to warn you that I'm armed to the teeth."

***

Ace's accent belied her location, and did not explain why she carried climbing equipment in her rucksack. She and Martha sat on the edge of the cave opening, dangling their legs into the hole. Martha took in the mycoforest towering around her and the domed cityscape visible through the spindly trunks.

"So, we're not in London, then?" Martha rested one hand on a fallen trunk - the pearly surface was silky to the touch and glowed faintly blue-white.

"Not even remotely. Not even the right galaxy." Ace peeled the foil wrapper from a protein bar and snapped it in half, offering one piece to Martha. "Travelling in time/space is like that, though. Physical distance doesn't mean a lot."

Martha nibbled tentatively on the mealy protein bar. "But I'm not travelling in time. Indigo doesn't have that capacity." Beside her, the timer was ticking away the minutes before she would have to teleport back to base and report that Indigo was jumping interstellar distances. She shifted slightly so that the time display was out of her field of vision.

Ace shoved half the protein bar into her mouth in one piece, then talked around it. "You must be, right? Because you said that every time you teleport, that stalactite is back. And you can't get out of the cave without smashing it. So you must be 'porting to the same place in space and time." She took a swig from her water bottle, and swallowed with some difficulty. "Hey, if we end up doing this again, bring some decent food with you. Something fried." She clutched Martha's arm suddenly. "Bring chips. Lots of chips!"

"But, wait a minute. I can't keep appearing at the same place in time - there'd be dozens of me all trying to crowd into the same area. It would be a paradox." Martha shook her head.

"There's ways and means," Ace said, loftily. "When you've done a bit of space/time travel, you get the hang of it."

Martha looked at her, nostalgia welling at Ace's nonchalance. "Don't you worry about the risks? A paradox is supposed to be a universe-shattering event."

Ace shrugged. "I know teleporting is tricky stuff: moving matter around is complicated. But maybe this is what Indigo wants - maybe it has stuff that prevents paradox? Time isn't as fragile as physicists make it out to be, you know."

Martha nodded her head slowly. "Wibbly-wobbly. Timey-wimey." Indigo was cobbled together from UNIT's stash of recovered alien technology, and what little they knew about the workings of the TARDIS. Who knew what they'd inadvertently built into the system? Beside her, the timer on the Indigo device reached zero and began to wail. Martha stood up, and shrugged into the shoulder straps. "Wait, what will I do when I teleport back? You'll have forgotten this whole conversation."

Ace grinned. "It's okay. I'll give you a code, so I'll know that you know me, even if I don't know you. Just say 'We're playing by Perivale rules.' I'll know what that means."

Martha let herself down Ace's folding ladder, and made her way to the jump point.

Ace leaned over the hole. "And don't forget the chips!"

***

Martha pushed her safety glasses up her nose, propped the step-ladder against the wall, and leaned hard on the stalactite. She'd lost considerable favour with the UNIT techs by returning without the promised samples and even more the next day when a suspicious smell of fish and chips hung about her as she buckled on the Indigo device. She should have told them about Ace. The contact would surely break all kinds of protocols, if UNIT had protocols for unexpected interstellar travel. But Martha didn't want to wait, or worse, be reassigned. There was a planet out there, she had the means to travel. She solemnly promised herself that she'd make a full report after this jump. Right now, though, she was here in the cave below the mycoforest, with a parcel of hot chips, and she was ready to investigate. The stalactite gave way, and she looked up through the rain of limestone rubble.

"Is there someone down there? If there is someone down there, I think it's only fair to warn you that I'm armed to the teeth."

Martha climbed up the stepladder, popping her head through the opening in the roof of the cave. Ace was crouched by the fissure in the ground, one hand inside her rucksack and a fierce expression on her face. Martha made a placating gesture with her hands. "It's okay, Ace. We've met before. We're playing by Perivale rules."

Ace raised her eyebrows, then grinned. "Why didn't you say so sooner?" She snaked a hand around Martha's neck and kissed her with an open mouth.

Martha pulled away in surprise. "Hold on, what are these Perivale rules, exactly?"

Ace let go, and scooted backwards. "We know each other, right? Perivale rules mean I like you, a lot." Her eyes narrowed. "Are you fooling with me, or am I fooling with me? Oh, I hate it when I set myself up."

Martha heaved herself out of the cave, and sat beside Ace on the spongy forest floor. "I don't think I was around long enough for either of us to be fooling anyone." She pulled out the paper parcel and tore a hole in one end. Ace leaned in hungrily, and grabbed a handful of chips. Martha put an arm around the other girl's waist and gave her a squeeze. "It was a surprise, that's all. Not a bad surprise." She had forgotten the glory of the unexpected, living under the weight of agendas and protocols and study propositions.

***

"This grove is my rendezvous point." Ace lay back on the lilac moss that covered the ground, her head pillowed against her rucksack. The swaying fronds of the canopy above made patterns across her face. "I've done my bit in the city, now I have to wait for the Professor to get back. Then I hit the detonator and our work here is done." The grease-stained paper from the fish and chips rustled in the gentle breeze.

Martha lay beside her, one arm thrown across her eyes. "Do you solve a lot of problems with explosives?"

"Disappointingly few." Ace turned over on her side to peer at Martha. "Is it any better with UNIT?"

Martha scrunched up her face. "Explosive isn't really a word I'd use to describe UNIT. They're efficient. They're very professional. I guess that's why I signed up with them - looking for other ways to explore the world. More ordered ways."

"That's not a bad thing, though, is it?" Ace elbowed closer, so she could rest her head on Martha's belly. She stroked the official embroidered patch on Martha's coverall. "I mean, you seem like you're in good with them, on the big projects and so on. It got you here."

"Yeah, and I'm sure they'd be thrilled that their seven figure budget has enabled the most expensive takeaway delivery service in the world. Maybe even in the universe." Martha sighed, and brushed some stray crumbs from the collar of Ace's jacket. "No. UNIT is everything they promised - pro-active, secure, important work protecting the Earth. It's just, I mean, look what Project Indigo's done to me - five jumps into the same cave and you have to help me find a way out. Maybe that level of caution is bad for me. Maybe I need to take more chances. Maybe I need a change." She grimaced. "Did I really say that? Working for UNIT was supposed to be my big rebellion."

Ace laughed. "Rebellions never turn out the way you plan them. Sometimes that's a good thing."

***

Her superiors took her resignation with considerable restraint and dignity, thanking Martha for her loyalty and courage, inquiring politely about her prospects for the future. Martha could hear the relief in their voices, and knew, as she closed the door behind her, that they would be marking her personnel file with all sorts of cautions. The worst crime in UNIT was to go rogue.

Martha knew she wasn't going rogue. She was looking for work with more autonomy and less predictability, where she still got to save the world, but didn't have to schedule approval from a superior officer. Perhaps UNIT would see that as a rebellion, but she knew people who would not.

On the night before she left for Cardiff, she did sneak back to the Indigo base for one last jump: unscheduled, unmonitored, late at night. She set the timer for an hour so she'd have time to put all the equipment in order and steal away between security sweeps.

A brisk breeze curled around Martha's ankles when she materialised in the cave - soft blue light filtered down through the hole in the ceiling. This time, the opening was already there, and moonlight filled the cave. She crunched over the fractured remains of the stalactite, and with an athletic jump and a mental thank you to UNIT basic training, she clambered out of the cave. The mycoforest was painted pastel in the light of the two moons, and Ace was nowhere to be seen.

Something crinkled underfoot, and Martha picked a note, weighed down with a foil-wrapped protein-bar. Ace's handwriting was bold and slanted - easy to read in the moonlight. The note said 'Good luck! Stick to the rules (you know the ones I mean.) A.' Martha folded the note up and tucked it into a pocket then turned back to the cave, ready to teleport back to Earth. Behind her, broad ribbons of smoke streamed up from the domed city. Rebellion was taking its own course.