Don investigates the role an ordinary US Postal Service mailbox played in one of the most damaging spy cases of the Cold War. And he examines a monstrous preserved head that may prove the existence of a legendary sea beast.

Don unveils the real-life story behind an impressive work of art. He examines a simple tire cover connected to a bizarre religious cult. And he visits the robot that may have saved thousands of human lives in the worst nuclear disaster in American history.