Mystery Island

The Skull's the Clue (1x15)

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The group seeks temporary shelter in a tree house, unaware Dr. Strange has it under surveillance, and soon find themselves besieged by the Apes. Upon learning from P.O.P.S. that the Apes are afraid of the Mud People, Chuck and Sue disguise Sandy as a Mudman, frightening their attackers away, but then they find their refuge is apparently caught in an earthquake -- courtesy of Dr. Strange -- and then a ghostly voice orders them to leave.