First World War intrigue drives this final mystery for Peter Cushing as the Master Detective. Surrounded by a solid cast, Cushing delivers a spry and energetic performance that at times defies his age. Cushing delights in Holmes' misogyny in his scenes with 'The Woman' and shares great chemistry with John Mills as an understated Watson. The delivery of poison gas into the tranquil homes of the UK is a devious plot worthy of Arthur Conan Doyle himself indeed and the detective's arrival upon the gas-making lair is exciting indeed. The only element that mars the story is the flashback structure of the movie and the frequent narration by Watson which robs the film of some of its tension. As a swansong for Cushing its indeed a solid farewell.