both of lovecraft's parents died in a mental hospital, and some critics believe that a concern with having inherited a propensity for physical and mental degeneration is reflected in the plot of "the shadow over innsmouth". it also shares some themes with his earlier story, "facts concerning the late arthur jermyn and his family". cthulhu, an entity from previous lovecraft stories, is the overlord of the sea creatures. the mind of the narrator deteriorates when he is afforded a glimpse of what exists outside his perceived reality. this is a central tenet of cosmicism, which lovecraft emphasizes in the opening sentence of "the call of cthulhu": "the most merciful thing in the world, i think, is the inability of the human mind to correlate all its contents."