This is likely to be a 7+ part story, updated once per week. Enjoy! :)

Prologue

"I'm bored."

"We could go save some planet somewhere? There's this nice little place in the Fallablindi region with a failing power supply. Shouldn't take too long. And technically, we have all the time in the universe. We have – well, yeah – we have the only time machine in the universe!"

"Aren't we lucky…?!" Jack said, rather derisively.

"Yes we are, Jack. Very lucky indeed."

"I'm still bored, though."

The Doctor sighed, rubbing the back of his neck. He was bored, too. He was bored of saving the universe, bored of being the good guy, being the hero. It wasn't that he wanted to be the villain – he just wanted to break the rules for once. Well – more than he usually did. He was feeling rather reckless.

"Jack – let's do something… naughty."

"Naughty, Doctor? ...Do you – do you mean what I think you mean?"

"I think, Jack – that depends upon what you think I mean!"

"I think you mean… sex?"

"What?! No, Jack! …Just… no. No." There was a long pause as the Doctor recovered mentally. He hadn't been expecting Jack to come out with that. Sighing, he began to explain. "The Seven Deadly Sins, Jack – you know them?"

"Uh – yeah… Lust, gluttony, greed… sloth… laziness – oh, wait, that's 'sloth'…"

"–Wrath, envy and avarice," the Doctor finished, a smile playing on his lips.

"Avarice being… pride, materialism, yeah – but what was your point? …Naughty, you said?"

"Wanna break a few rules, Jack?" If he was going to break the rules – these were the ones. He opened his mouth in a sideways grin, running the tip of his tongue over his teeth.

Jack grinned too, trying to divert his mind from thinking about how suggestive that gesture was. He leaned forward on the Tardis console, eyes twinkling. "Sure."

"Good. One week challenge. Every day for a week, we… practise… one of the deadly sins. Starting with 'vanity', I think."

Laughing at the strange but innovative idea, Jack nodded.

"From tomorrow, that is. We'll just have to… I dunno – save that planet in the Fallablindi region today. Ah, well. Cest la vie. And allons-y!" They grinned at each other, the Doctor setting a dial on the console panel, hammering the Tardis into life.

Read on! :)