Sherlock
Logic
Riddle #67
Four logicians are imprisoned and given a chance to go free. They are lined up so that Logician 1 sees 2 and 3, Logician 2 sees 3, Logician 3 sees no one, and Logician 4 is behind a wall and sees no one. Two red hats and two blue hats are placed on their heads. They cannot turn, speak, peek, or touch the hats. If one logician can state their hat colour with absolute certainty, all four go free. Can they escape, and who speaks?
