One of the players finds the Devil’s mouth, which tries to trick Jiu Shi into opening another box with a Devil part in it. The players restrain themselves from opening boxes but find that they can’t eat unless they open a box. Someone finds a stethoscope which can be used to listen for the Devil in the box, but can only be used 3 times a day, while Jiu Shi’s hearing can be used 2 times a day. (Source: frankly at MyDramaList)