Accused of fraud, Ivan Lausman aims to end it all by driving his car into a river. When he's washed up 10km downstream, alive and well, the Aquarians know he's a land-lubber with a residual Aqua gene.

Inspector Jara and Trpelka, the officer assisting her, investigate what happened to Ivan Lausman, but they are unaware that the nixes, or Water People, are also after him and he has gone into hiding.

Jara makes a breakthrough when she receives another set of photos. Lausman attends a nix history lesson by Dr Magda Mrackova and learns about the 'magic water' of Vysehrad lake, hidden beneath Prague.