Le cercle vicieux

A young artist, occasionally gigolo ,marries an older woman for her dough;however, he has always an affair with a young girl.The wife has a face-lift to look younger and prettier,but it's the straw that breaks the camel's back:the marriage is on the rocks .The young mistress is killed in a car crash and the dead body is impossible to identify .So she could easily pass for his wife .So what about killing her and burying the corpse?But a stepdaughter is to be reckoned with..