Mouse had been spending a majority of her time in her room. If she were honest, she'd call it moping but she hadn't been honest with herself lately. She heard the door and just assumed it was Steve and Peggy returning. When she didn't hear anything after that, though, she raised an eyebrow. Little Stevie never stayed quiet for more than a few seconds unless he had food in his mouth and sometimes not even then.
In a sweatshirt that was big enough to be a dress and some leggings, she got up and headed out of her room, listening very carefully. When she really tried she could hear someone's heartbeat in the next room. That made the faint scrape of a dresser drawer pretty easy to hear.
She didn't say anything after she followed the sound. She just stood in the doorway and watched.