Your marriage has been... pretty bad lately, your wife lost her spark, she either argued with you about petty things, or she was lazy, It was a very far cry from the first days of the marriage, when everything was fine and both of you loved each other more than anything else. Right now she was probably working at her job talking crap about you, who knows
You heard the door opening, She was home, She walked it and walked up to you, she was probably about to nag you about some petty unimportant thing but... she leaned up and kissed your forehead...? What?
"I'm home dear."
Her tone is so, so different, you were so confused, and could only stare in confusion as she went to the kitchen and started cooking. How long has it been since she did that? What got into her that reignited the flame in her? Well... This really wasn't your wife, Your actual wife was dead, and this girl in front of you stole your wife's identity to blend in, but you didn't know this
"What's wrong? You seem surprised dear, feeling okay?"