It's incredibly well-acted: The intensity and fear shading into disappointment and eventually a broken heart, for both of them. You can see Steve getting smaller under her gaze, but the fear goes away and the Fiona part goes away and pretty much it's just Steve, feeling like a complete asshole for lying to Debbie, and then even that's gone and he just feels very cold and very alone and very much like a complete fraud. All in the eyes. So Debbie fucking bounces before she starts crying with frustration, and Candace is about to invite her for dinner before she realizes she's gone: "Oh, shit. I liked her."
Joan Cusack takes the random parts of this paragraph and knits them into something that is truly beautiful: She finds Frank hiding in the hall closet and worries that he's taking a crap in there, when really he's trying to get up the nerve to call Monica, even though he knows she hates him and can't figure out a way to make her come do this money thing with him. He tries to get Sheila to call for him -- fake Monica out with some kind of fake prize -- but Sheila, already feeling pretty weird about the whole Frank Situation given last week and earlier in this episode -- thinks (correctly) that he's fucking around on her, so he has to chase her upstairs and under the duvet where she's crying and eventually offer to quote, "dress up any way you want, no safety word." Old Sheila, she snaps to.
They call up Monica and pretend it's some promotional thing where she won $100 and a teddy bear for showing loyalty to this grocery store, which Sheila writes down for later, and the whole time she's making these insane, gruesome, beautiful Bacon-esque faces, and Frank's getting more and more uptight and mean as the call goes on, and whatever it kind of degenerates into acting tics for everybody at once, but they've got Monica where they want her.
Steve finds Debbie sitting in the snow at lakeside and begs her to let him take her home, but she does more of that precocious stuff the actor can't quite pull off ("I'm not supposed to take rides from strangers, and it's clear that you are a stranger") before pointing out that the many things she's maybe going to tell Fiona, aside from his false identity, now include the totally gross kissing of him on the mouth by his mother. "Life gets really complicated when you're an adult," he starts, and then gets real: