Gaslight - Full Movie (1940)

Twenty years removed from Alice Barlow's murder by a thief looking for her jewels, newlyweds Paul (Anton Walbrook) and Bella Mallen (Diana Wynyard) move into the very house where the crime was committed. Retired detective B.G. Rough (Frank Pettingell), who worked on the Barlow case, is still in the area and grows suspicious of Paul, who he feels bears a striking resemblance to one of Barlow's relatives. Rough must find the truth before the killer can strike again and reclaim his bounty.

my two cents:

the 1940 British psychological thriller that introduced the world to the concept of 'gaslighting.' Today, it is common for someone to say, "Are you being gaslighted?" Talk about head games... Here's a very telling quote from the movie at 01:07:43: "and every time he lights the gas up in that room, so it dims down here." To me, gaslighting is witchcraft; using words to cast spells on the mind through the spirit of suggestion, to hide the truth so those who are ignorant to the truth of deceptions will participate in covenants with the wicked.