In the garage, Lydia pounds on the door to the house. She can't get it open. And the car engine is going. She starts gasping for air. Then sobs. Emily hears knocking in the hallway. Dominic hears it as well and goes down the hall to the garage door. Emily runs after him. Dominic gets the door open and Lydia falls into his arms. He turns off the car and tries to open the garage door. Lydia says it's not working. Emily goes to find the garage door opener. The door opens. What I think actually happened that night is this: Dominic was waiting outside the garage door. As Lydia pointed her remote, he was using his to close the door. And he nipped in under the door as it was closing and she was leaving. He turns the engine back on. And then pulls the cabinet over just to make it appear like it was maybe just an accident. A safety net in case someone found Lydia before the carbon monoxide had done its job.