Torchwood, Series 2

Tosh:
You said we weren't allowed to use that again.

Jack:
It's just a mind probe.

Ianto:
Remember what happened last time you used it?

Jack:
That was different. And that species has extremely high blood pressure.

Ianto:
Oh, right, their heads must explode all the time.

[Gwen looks up, wide-eyed in shock]

Gwen:
Jack, you can't do this. What if you're wrong? If she is human, it'll kill her.

Jack:
I'm not wrong. We have to find out what she is.

Tosh:
Take it easy, Jack. Stop at the first sign of trouble.

Ianto:
Or at the first sign of exploding.