Jack Harkness stepped out of the TARDIS and saw the entire area seemed to be covered in plants. The Doctor followed him out, pulling on his long brown coat.
"It's all coffee," he informed the Captain. "Half the planet is covered with coffee plantations."
Jack looked at him with a mixture of confusion and a wistful sadness. He had no idea why the Time Lord had brought him to this planet and coffee reminded him of a too recent lost love.
"Why are we here?" he asked, trying to disguise the emotion in his voice.
The Doctor smiled warmly at his travelling companion.
"They use coffee as a currency on this planet," he told him. "The really interesting part, and the reason we came here, is the word they use for measurements of coffee."
Jack stared out at the plantation and waited for the Doctor to continue. He wasn't really that interested in what the units they measured the coffee were called. At least, he thought he wasn't until the Doctor said it.
"The units are called Yanntoes."
The Time Lord couldn't help but smile at the look of realisation that spread over Jack's face. He didn't fail to miss the tears as they fell, unbidden, from the Captain's eyes.
"He's remembered Jack."