This is a photo from "House Hunting." It is the penultimate episode of Being Human.
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The roommates realize they aren't the only ones having issues leaving the house on Being Human. "House Hunting" is the 12th episode of the fourth season.
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Being Human Season 4 Episode 12 Quotes

What happens next is that we're moving into my apartment. Together.

Nora

Sally: Aidan, are you asking me to move in with you?
Aidan: Technically, I think I'm asking you to haunt me.