Case 059
The Swapped Envelope
A sealed envelope was replaced with an empty one.
Rule: exactly one suspect is guilty. The guilty suspect lies. Every innocent suspect tells the truth.
Harper
“Either Rowan or Lane is guilty.”
Kendall
“Lane and Hayden are both innocent.”
Rowan
“Lane is innocent.”
Lane
“Kendall is innocent.”
Hayden
“Harper is guilty.”
Who is guilty?
Solution: Harper
If Harper is guilty, Harper's statement is false and every other statement is true. Testing the other suspects creates at least one contradiction.