P.O.W.
"If you cried, you died."
"How long were you held, Doctor?"
"Two years. I'd lost the TARDIS. I was caged with eighty other men; anyone who wept was removed."
"Why?"
"To harvest our tears. We were tortured, physically and emotionally, for our tears."
"Why your tears? Didn't your captors cry?"
"No, Tegan, they couldn't, and they needed tears for their national dish."
"But dead men can't cry!"
"When they'd cried themselves out, they were discarded."
"You never cried?"
"I knew the TARDIS would find me."
"How could you never cry?"
"I wanted to live."
"But Doctor..."
"I wanted to live."