The series starred Martin Milner as Karl Robinson, the survivor of a shipwreck who found himself, his wife, and two sons stranded on a volcanic island. In one of her first acting performances, Helen Hunt co-starred as a young girl who was stranded on the island from the same shipwreck who was taken in by the Robinson family. Befriending the Robinsons was Jeremiah Worth (played by Cameron Mitchell), a sailor who had survived on the island alone for seven years following an earlier shipwreck.