Doctor in the House S04E12 - A Night with the Dead

Bingham is anxious to propose to Dr. Mary Parsons and does so in the mortuary where she is working, but by accident slips the ring onto a corpse's finger. Mary still carries a torch for Duncan, which angers Bingham. Dick has bet Duncan he can't stay the night alone in the mortuary so he, to win the bet, and Bingham, for revenge, dress as ghosts to scare him. Duncan sees through the trick immediately and sends them away - but another corpse is apparently stirring under a sheet. It's Mary, still after Duncan.