You state that Marta’s lying doesn’t make her “bad,” but her vindictiveness and cunning add a layer of moral complication.

Personally, I don’t see her as being vindictive in this scene. At this point the only way not to lose (there really isn’t a “winner” since people have already died) and to have Ransom face the consequences of his actions is for him to admit his guilt. And the only way to do that is to make him think the consequences are negligible and easily surmounted.

The true moral complication comes from the final scene where she’s standing on the balcony drinking from the “My House, My Rules, My Coffee” mug and staring down at the Thrombeys.

Which in turns brings us to the real question? Just when did she recognize the game and begin to build her own pattern? After Fran’s death? When Ransom appears to “help”? After Harlan’s injection? Before?

It seems, after all, that everyone knew the consequences of Harlan getting the wrong medicine. But who provided the impetus to make sure that information was known?

Just how good a player was she?