I wondered where the dramatic hook was, too. So, people realize "hey aren't you supposed to be dead?" And then what? That's a situation, not a story premise, but the premise is in the link:
“Determined to reclaim their lives and start over, they slowly come to realise that they are not the only ones to have been brought back from the dead,” runs the show’s promo material. “Their return augers torment for their community when a series of gruesome murders bear a chilling resemblance to the work of a serial killer from the past.”
So...an undead serial killer is running amok and the "good" dead people must stop him? Only a ghost can stop a ghost! Yeah, that could be fun.