Donna was pretty sure the Doctor would not approve of this. She certainly hadn't meant for it to happen. Really, she'd been making innocent mistakes all day, referencing works which were not yet written. Somehow she doubted, though, that the Doctor would categorize this as an innocent mistake. 'Oh, well, it's not like stopping now is going to make things any better,' she thought to herself before becoming quite distracted by the world's most famous mystery novelist curling her fingers and circling her thumb around Donna's clit.
There was something deliciously wrong about it. Agatha Christie's hand was up her skirt, doing some excruciatingly wonderful things. This was the same talented hand that had written Murder on the Orient Express...or rather would write it in future. Agatha muffled Donna's groan with a searing kiss as her fingers pushed Donna over the edge, clenching muscles around the writer's probing digits. The two women parted, breathless and wild-eyed. 'I really didn't mean to...' Donna thought when coherency returned to her. 'So much for comforting words and an encouraging hand squeeze.'
Once speech found them again, Agatha gave a sly smile to Donna. "You're right. I am better off without him."
"I'll say," Donna breathed.