The Secret was a mysterious unidentifiable thing that was concealed in a wooden box. It is found in the Thieves' Den of the Crossroads, where it is in the possession of a ghostly thief formerly known as Kevin. It was one of ingredients needed to complete the diet of the senses. It served as the opposing counterpart to the "fifth sense" of the Feast of the Senses, due to not being able to know what is inside the box.