Geronimo Stilton is a mouse who manages the most famous newspaper on Mouse Island called "The Rodent's Echo". He enjoys writing books and spending time with his family, which includes his sister Tea and cousins Benjamin and Trampita. In the book "Geronimo Stilton and the Ghost of the Subway", Geronimo and his friends investigate a reported cat ghost in the subway tunnels of Ratonia but discover it is just an experiment by Professor Voltio.