"Calculated studies require extra effort," he explained, reaching up to slowly undo the buttons on Jack's shirt. There was more effort involved in making sure his hands didn't shake than he wanted to admit, but he was, surprisingly, nervous. Things were going well. Surprisingly well. Much better than they usually did with him and Jack, especially lately.

"You wear more layers than I do," the Doctor commented, tracing his forefinger along the white undershirt below Jack's blue shirt. "And that's saying a good bit, actually. Never could figure out how many shirts worked under a suit. And I've been trying for a while."

He slid his finger down Jack's sternum slowly, as though making a careful point, but mostly to feel the warmth of his companion against his skin.