Trivia: Professor Plum reveals that he works for UNO, the United Nations Organization, in a branch called WHO, the World Health Organization. As such, he works for UNOWHO (You Know Who).
Trivia: Professor Plum hypothesizes to the group that the brandy was poisoned. In the original Cluedo board game, poison was included among the possible weapons, and later re-introduced in 1990's game Clue Master Detective.
Trivia: Not a mistake, just a neat little fact. When the film was being shown at cinemas, only one ending was shown. Different venues had different endings.
Trivia: Miss White's "flames on the side of my face" line was ad-libbed by Madeline Kahn.
Answer: It depends on which ending you subscribe to. It could have been Scarlet to hide evidence of her brothel. It could have been Mustard to hide evidence of his affair with Yvette. Or it could have been White who wanted to destroy pictures of Yvette "in flagrante delicto" with other men (reminding her of her husband's infidelity).
Macalou