This is a Supplement to Locked Room Murders, Second Edition Revised, by Robert Adey, the standard bibliography of mystery fiction featuring locked room mysteries or other impossible crimes. The previous volume, also available from Locked Room International, covered the field from the beginning of the detective story until 1991. For over 25 years fans of the impossible crime have been waiting for an updated edition. This Supplement brings the combined bibliography up to date through 2019 and also includes older items not included in the previous editions. There are over 1,150 additional entries listed here that identify novels, short stories, TV shows, movies, and other media with puzzling impossibilities.