Sapphire & Steel (1979)

Season 1: Episode 3

Sapphire and Steel investigate the upstairs hallway after Rob sees a pair of ghostly soldiers on the landing. Unbeknownst to them, a living pool of light has escaped from Helen's room and now lies in wait in a portrait at the top of the stairs. Sapphire walks right into the trap and disappears from the house. Only faintly able to communicate with Steel and Rob, Sapphire tells them she is stuck in a freezing cottage with the sensation that something sinister is there with her. Steel and Rob discover that Sapphire is trapped in the portrait and must work quickly to avoid losing her.