Who said "I wonder if you're all mad."?

This quote is attributed to Armstrong.

I wonder if you're all mad. - Armstrong

"I wonder if you're all mad."

Armstrong Fear

Character in And Then There Were None

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"We are none of us infallible."

"The innocent suffer with the guilty."

"Each of us has something to hide."

"We deserve what comes."

"Face your fears with courage."

"You can't live your life in fear."

"Snakes. Why'd it have to be snakes?"

"Fear is just another obstacle to overcome."