So this is a major spoiler but given the chronological sequence of events, it all makes sense (as opposed to some who think not). Chronologically, it resembles Now You See Me more than Wild Things.
Man dates rich women, possibly killing them for the money. Man killed woman with two daughters (D1 and D2), and dragging mother to be buried in front of daughters.
Man marries very rich woman. Man kills rich woman in pool. Woman's Daughter (D3) does not inherit money.
D1 and D2 plots for revenge (possibly for money but looks more like revenge story). The plot involves D1 getting close to D3 to sub-plot killing D3's step father, Man. D1/D3's plot involve 1. D1 marrying Man 2. getting a woman to be the fall guy for D3's crime when she kills Man.
D3 thinks she is approaching vulnerable D2 and sets things in motion, not knowing that she is actually the real fall guy. The rest of the story is how the movie runs from beginning.
Man dates rich women, possibly killing them for the money. Man killed woman with two daughters (D1 and D2), and dragging mother to be buried in front of daughters.
Man marries very rich woman. Man kills rich woman in pool. Woman's Daughter (D3) does not inherit money.
D1 and D2 plots for revenge (possibly for money but looks more like revenge story). The plot involves D1 getting close to D3 to sub-plot killing D3's step father, Man. D1/D3's plot involve 1. D1 marrying Man 2. getting a woman to be the fall guy for D3's crime when she kills Man.
D3 thinks she is approaching vulnerable D2 and sets things in motion, not knowing that she is actually the real fall guy. The rest of the story is how the movie runs from beginning.