Dark Shadows - Season 4 Episode 59 DS-334

Burke and Dr. Woodard tell David that they didn't find anything in the Old House basement. David decides to tell them about the secret room in the mausoleum, breaking his promise to Sarah. As soon as Burke and Woodard leave, the window to David's room bursts open, and David fears that it's Sarah showing him her anger. At the mausoleum, David takes Burke and Dr. Woodard to show them the secret room, but the door will not open. Later, David finds Sarah's flute.