Based on the Dark Horse comics, SYFY's Resident Alien follows a crash-landed alien named Harry (Alan Tudyk) whose secret mission is to kill all humans. In Season 3, Harry is vowing to work with General McCallister (Linda Hamilton) to rid the Earth of the Grey aliens – a task made more difficult when he discovers that the Grey Hybrid Joseph (Enver Gjokaj) has taken a job in town as the new Deputy. Joseph isn't Harry’s only obstacle – Harry struggles to balance business and his personal life when he falls in love for the first time.

Meanwhile, Asta (Sara Tomko) and D’arcy (Alice Wetterlund) move in together and struggle to discover their purpose in the world, Sheriff Mike (Corey Reynolds) and Deputy Liv (Elizabeth Bowen) continue their quest to find out who killed the Alien Tracker, and Ben (Levi Fiehler) and Kate (Meredith Garretson) are forced to deal with the subconscious repercussions of their alien abductions.