But the Christie adaptations that followed — “Death on the Nile” (1978), “The Mirror Crack’d” (1980), “Evil Under the Sun” (1982) — were half-baked suspense films that felt, collectively, like the fading embers of a genre.
As well as being a sparky and sympathetic character in her own right, Marta becomes a litmus test for the morality of those around her, just as her broken phone screen with its spider-web splinters ( The Mirror Crack’d , indeed) mimics the giant circular sculpture made entirely of knives that has pride of place in the Thrombey mansion.