Continuity mistake: Right at the end when the man takes his mask off, a strand of blonde hair hangs out from the back of "his" head. In the next shot the hair is dark brown.
Continuity mistake: When Lionel Twain is leaving the dinner table, in one shot his left arm is up, but then down in the next.
Answer: According to the script, she is mouthing "I think he's lying."