He hadn't meant to do it – that was not to say that it was an accident. One minute Missy was cussing and jumping about, going on and on about the tiny-brained-insects that controlled the planet and how easy it had been to conquer then and why wouldn't he just let her have a little fun – then the next she tipped backwards.

It was slow motion after that.

Instead of retreating to his mind-Tardis to have a good ol' chat with his blackboard about what to do, he'd stared. Stared forever at the toppling image of Missy falling silently off the edge of the crystal cliff.

This planet had always been beautiful – no more so than right now. They were quite literally perched at the top of the world, standing on the shimmering mountain range of treacherous peaks and unforgiving surges of opal. It was folded through the crystal base and screamed with a billion colours as the pair of stars set toward the horizon below.

The Doctor lunged forward. Mid-flight, arms outstretched, his fingertips brushed over Missy's as she started to drop out of sight. He had no idea if he'd jumped too far, if he too would clear he edge and spiral down after her. All he thought of was making sure he found her hands. Somehow he did. Fingers tangled together and caught firm. His chest hit the edge of the cliff. Solid. Safe. A moment later Missy's weight was pulling him over. He groaned, resisting.

It worked.

Time caught up with them and the Doctor grinned madly.

"What's so damn funny, you mad bloody-"

The Doctor stopped her mid-rant. "The look on your face," he replied, letting her swing at his mercy for a moment before he set about hauling her back up to safety. It was a bit of an awkward scramble but eventually he succeeded and the two rebel Time Lords – aka the most dangerous things set loose on the universe, sat quietly on the edge, looking over the world.

"I thought you came here to kill me?" Missy said quietly, choosing not to acknowledge that the Doctor appeared to have one of his ridiculously long, stick-insect arms around her.

"Saving the indigenous people of this planet from your reign of tyranny and killing you are not the same things," he pointed out. "Besides, you're always trying to kill me – rather unsuccessfully, I might add."

Missy was trembling and considering the elevated temperature on the desert planet, it wasn't from the cold. He wasn't quite sure how many regenerations Missy had left. Maybe she wasn't sure either. He supposed things got a bit hazy when the time vortex resurrected you. A fall like that... Death was death, even if you woke up afterward.

In a rare moment of silence, Missy let her head tumble down against the Doctor's shoulder. He dragged her closer and for a few minutes they were the same silly, rebellious children getting into mischief, pulling each other out of it, rampaging across time and space as if it existed solely for their amusement.

The Doctor knew that the moment had passed when she shoved him to the ground and made a play for his Tardis.

"Stop bloody smiling! It doesn't suit your eyebrows!" she snapped at him, circling the blue box.

He kept smiling. He always would.

By some accident of the universe, they were friends.