Do you know any other Ethans? "Yeah. You're not mad, are you?" she asked, wrinkling her brow with worry. "He just showed up here and I didn't know what to do so I just let him in."
On some level, Stacey knew that there wasn't a good reason for Sam to be upset--she hadn't spoken to Ethan since the day he had moved in and before that she hadn't seen him in years. She also told Sam absolutely everything usually; sometimes she didn't tell him things right away, but she always told him. Like on Mothers' Day when she'd been sad about her miscarriage, she had kept it to herself that night, but then talked to him about it the next day. The only thing that she wasn't bringing up yet was her fear that he didn't want to marry her one day. And like everything else, Stacey was sure that it was going to come up one day.
But on another level, this was Sam's place, too, and he was well within his rights to get pissed off by her ex-boyfriend being over when he wasn't there, even if it was just for a few minutes. Especially given that Ethan was currently naked.