Oh yeah, I see! It must have been a simple coincidence that Freddy knew exactly when to slip into the house with the knife, ready and waiting for their return from the theater when hubby would have his guard down, probably half-drunk from drinks afterwards at the pleading of the Mrs.
So, she had a real swingin' time in the end.
Actually, the attack took place outside the house and being a tennant of theirs, he was pretty familiar with his victims routine.