Murder on the Diary Express (starring Detective Sargent Silly from Mobsters City) was written in STAC by James L Mathews of Power Diskmag/Power PD/Top Byte software for Silly Software. It was written especially for the Silly Games Pack which included Silly Reels and Grannies Garden - and not forgetting the Major Bumsore Dancing Teeth demo
I never personally completed it myself so I can only advise you track down James himself or hope to find someone who has completed it.
By the way - I know who the murderer is in this game because James told me
I can tell you if you want to know