Not the be overly cynical, its a lame ploy.
The movie was suspenseful enough in parts, and bonus for not relying on gory crap, even if it fell flat in overall. But the killers, when Liv tyler asked why you are doing this...how lame wasnt it that she got the answer: "because you were home..." I mean, really?
Btw, why the heck did she survive those multiple stab wounds?