Case 333
The Vanished Key
A locked evidence cabinet was opened without permission.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Quinn
“Either Harper or Drew is guilty.”
Harper
“Neither Taylor nor Drew is guilty.”
Taylor
“Quinn is guilty.”
Hayden
“Neither Harper nor Taylor is guilty.”
Drew
“Harper and Hayden are both innocent.”
Who is guilty?
Solution: Quinn
If Quinn is guilty, Quinn's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.