I think it was ok to let Karl go. I think Sawyer might have done it just because he didn't think they needed any more info about the others because they weren't going back for Jack anyway.

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" I push this button every 108 minutes, I don't get out much."

"Theres a time for living low down, theres a time for getting high. A time for peace, a time for fire. A time to live, a time to die."

The real art of conversation is not only to say the right thing at the right time, but also to leave unsaid the wrong thing at the tempting moment.