The fourth season starts with Harry and his baby Bridget stuck in prison on the Grey Moonbase, while a shape-shifting Alien called a Mantid has taken over his body on Earth passing himself off as the real Harry Vanderspeigle. Harry manages to escape the Greys and arrives back on Earth for a showdown with the Mantid Alien, but soon finds he may not have what he needs to finish the job. Asta and D'arcy struggle to keep a secret from Ben and Kate, who are both desperate to find answers to what has been happening to them. Sheriff Mike and Deputy Liv attempt to solve some mysterious deaths in Patience that Sheriff Mike is beginning to think aren't caused by anything human.