He told me he is a knave
On the island of knights and knaves you meet A and B. You did not hear B speak, but A tells you: "B said that he is a knave."
What is A? Can you determine what B is? Explain carefully which of the two you can pin down and why the other one stays open.
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Could B actually have said "I am a knave"? Test both possibilities for B first.
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