Of what impending danger does Christian warn his family

In the first part of Pilgrim's Progress, Christian recieves his calling from the Evangelist and leaves his wife and children behind in the City of Destruction. He effectively maneuvers his way through the Slough of Despond, passes under the Wicket Gate (the gate through which the elect must pass, beginning their journey to Heaven) and soon comes to the Interpreter's House, where he learns to think metaphorically. After leaving this enlightening place, Christian sheds his burden and receives the garb and certificate of the elect from some angels. His next stop is the Beautiful Palace.