In an unknown place, children are trapped in darkness. Their kidnapper is dead and you must find the hiding place and save the children before it's too late. "The Secret of the Mark" is the second part of Maria's trilogy. 50 Clues® is an award-winning puzzle and mystery game that offers the experience of an escape room, which can be played at home. An application on your smartphone will track your progress and provide hints if needed to reach the solution of the mystery.