The hand-in-a-jar was just one of those things. Like Myfanwy, or Jack Harkness, you just didn't talk about it.
On the other hand (not in a jar) when it came down to a team member or a hand and Jack went for the hand…the rules were temporarily switched off.
"Okay," said Owen as Jack set it down on the desk. Its fingers twitched. "Okay. Jack, mind telling us what the hell is with the severed hand in a fucking jar?"
Jack said nothing, picking up the broken jar with a frown.
Tosh fidgeted. "It's obviously important. But why?"
"Yes," said Jack tersely. "It is important. It's very important."
"But what is it? Is it even a hand or some – alien – thing?"
"It's a hand," Jack said, turning the container's wreckage over in his hands.
"But whose?"
The fingers of the hand twitched innocently. Jack looked at it and frowned. Finally, he said, "It belongs to an old friend."
"Do your friends often lose their hands?" Owen snarked, and Tosh hit his arm.
"Shut up, Owen."
Gwen stopped chewing her lip, arms still crossed. "Where is he now?"
Jack paused. Then shrugged, and picked up the hand, almost cradling it. "No idea," he said, and there was a strange note in his voice that none of them had heard before.
And just like that, it went back to being one of those things – the things they didn't talk about.