Charlie Chan – The Man Who Murdered Santa Claus. 1946.

Charlie and #1 son are helping to plan for the annual police Christmas party. Carols are sung at the piano. The party takes a less than festive turn when a man in a santa suit is found dead. Charlie gets busy with checking on clues, and is soon on the trail of his suspects. A dark colored van is a major clue, but it seems to have vanished. As Charlie and #1 son move in, a man with a sinister voice fills them in on motives for the killing. With some decisive action from Charlie, the bad guy is taken down, and the party can resume.