Before watching the movie:
How often can a murder victim solve their own murder (aside from ghost stories)? The idea doesn’t seem quite as unusual as it’s hyped up to be for this film, but probably more of that is from 60+ years of speculative fiction covering the territory than from promotional overhyping.
Doctors tell the man there’s no antidote for the poison he took, but I wouldn’t be at all surprised if the investigation into the crime leads him to one. I’ll be interested in seeing how the film handles the process of his dying. I picture a poisoning victim as someone too ill to run around town questioning people.