Locked Dungeon Escape

Walking late at night on a dark street, you heard a pleasant voice that sings. You went on to voice and soon saw the princess sitting on a bench and sings. The guards saw the princess, as you approached her and decided to imprison you into prison. Now what to do if a lattice door locked? Rather, look for things and make a plan with which you will be able to escape from prison. Explore the room and try to found objects interact with each other, until you get the result.