Based on the Dark Horse comics, Resident Alien follows a crash-landed alien named Harry and his life on planet Earth. The fourth season starts with Harry (Alan Tudyk) and his baby Bridget stuck in prison on the Grey Moonbase, while a shape-shifting alien called a Mantid (also Alan Tudyk) 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 (Sara Tomko) and D'arcy (Alice Wetterlund) struggle to keep a secret from Ben (Levi Fiehler) and Kate (Meredith Garretson), who are both desperate to find answers to what has been happening to them. Sheriff Mike (Corey Reynolds) and Deputy Liv (Elizabeht Bowen) attempt to solve some mysterious deaths in Patience that Sheriff Mike is beginning to think aren't caused by anything human.