Impossibly slow-moving murder mystery. Amateur theatrics, manor houses, ineffective detectives in trench coats... it's very British. There are at least twelve major characters in it. After 15 minutes things are moving so slowly, that a viewer begins wondering "Shouldn't someone be dead by now?" But you still have half an hour to wait. Finally, with twenty minutes left in the movie, things haven't even gotten interesting, and no one stands out as a culprit or as a character. You don't care about the victim, so you sure won't care who did it. The editing is inept. Scenes don't even develop before some intrusive, distant snippet is inserted. The actress playing Marple doesn't look shrewd, instead looking addled most of the time. She might be the least effective actress to play Miss Marple.
It's a mess.
It's a mess.