Josh and Nora find their perfect couple-hood in peril when Conner and Brynn's father, Liam, shows up again. Liam has been systematically killing the remaining diseased vampires in Boston and, by chance, he runs across Aidan, who gives Liam's crew quite a beating. Angry and wary, Liam follows Aidan home only to realize that Aidan lives with Nora and Josh!
Since, in his own way, Liam is trying to bond with Nora, Liam tries to talk Nora into killing Aidan, despite Josh's obvious misgivings. Josh is horrified but Nora's distrust of Aidan has been growing with each passing day. She thinks of Aidan as a walking time bomb and also seems to be developing a natural werewolf's dislike for him too.
To Nora, Liam's offer at least deserves a listen. Once Josh realizes that he'll have to deal with this situation on his own without Nora's help, he decides to confront Liam in person. Josh shows Liam that he's not a punk by threatening to kill Liam with silver bullets if he doesn't leave his "family" alone, so the two of them come to a terse, but manly (wolfly?), understanding. Liam even brings Erin home to Nora and Josh—much to Erin's disappointment. Nora, however, doesn't seem to be done with her growing hate for Aidan.
Things only get worse for Aidan when the ghosts of the two party girls he killed in a bender with Henry last season suddenly return to haunt him. They tell Aidan that they abandoned trying to find their door in order to torment him for as long as they can. Starving and miserable, Aidan finally does the unthinkable and starts extracting extra blood from Kenny, the bubble boy, to sustain himself. It seems to be the perfect plan but things get hairy when Aidan confesses to Josh and Nora, which only makes Nora hate him more.
Surprisingly, Kenny suspects that Aidan is a vampire very quickly but he has no proof so he starts conducting amateur tests and finally confronts Aidan about it. Aidan, of course, denies it but, later, he falls asleep in Kenny's room and, after a disturbing nightmare that might have been caused by his ghostly tormentors, he wakes up with his vampire nature showing. Kenny sees it all.
Sally's new job ends up being more than she bargained for. Sure, it's grisly dealing with dead bodies but Sally completely forgot that she'd also be dealing with the ghosts of those dead bodies. Since all the ghosts can tell that Sally can see them, they ask for her help but Sally refuses, thinking she'll just mess things up more. Sally gets quite a shock when Linda, the ghost of Max's mother shows up and, even worse, tags along on Max and Sally's first date. Sally and Linda quickly come to an impasse: Sally wants to date Max but Linda will have none of it. They fight at first but, in the end, Linda's motherly love wins out and she supports Sally and Max's budding relationship.
What goes on behind the scenes for the score of Being Human? Watch this interview with composer FM Le Sieur.
Sally makes a major sacrifice to keep two of her roommates from killing each other €“ a move that will change all of the roommates€™ lives forever.
The cast reflects on how the show has changed them over the 4 seasons.