The Mysterious Lake is an underwater adventure of ten-year-old twins Josh and Katie, who are searching for their neighbour’s little terrier, Miffy. By accident, they fall into Otriana, an underwater world, and meet Nepta, a boy about their own age, and his sister, Coralie, who is much younger.
Republican President James Whitcomb is in his third year in office. With the next presidential election fast approaching, his chief of staff has decided to begin his reelection campaign by making appearances across the country, speaking directly to the voters, without the filter of the hostile mainstream media.
It has been twelve years since twins Josh and Katie Jenkins were unwittingly propelled into the underwater world of Otriana while searching for their neighbor’s dog. After meeting Nepta and his sister, Coralie, who help the twins escape Otriana, their adventures eventually lead them to be accused of murdering Nepta and Coralie’s father. Now, Nepta wants to visit the earth world to see the twins again. But there is only one problem: Coralie wants to accompany him and she is out for revenge.