Because the powers that be (Earthly ones, not supernatural!) noticed that she'd been moved after she'd died, though why that should be particularly suspicious I don't know as she was on her last legs anyway. & the cough was daft, as souls wouldn't have illnesses (anyway, a hefty dose of antibiotics would soon see to that!)
A load of hokum, but I loved it - glad they focused on Bill Paterson again & not those Scooby-Doo sidekicks from the last series.
But why isn't it on next week?