For the purposes of this story, the girl's name is Susan.
He's brought into that room, filled with people and he doesn't know. He doesn't know what they're prattling on about, and he doesn't know who the little girl is, with the dark hair and eyes too wise for her age. Until they say he has to choose. Then they give him time and start discussing her like she isn't there. Her name's Susan. Mom had an affair. Mom and Jack don't want her anymore, she's too sad and as they talk she has a look, like she doesn't want to go back to Jack anyway, but is at the same time sad that they don't want her. Then he looks at the paperwork in front of him, and the paperwork sitting next to him. And Frank makes a choice. The authorities think Mom and Jack kept the girl after all. Mom and Jack think they took her with them and focus on worrying about Frank. She's really eating dinner at a hotel with Frank.
When he pretends he's researching Pan Am for his school, she's right there listening. He takes her everywhere. He says his parents made him take her with him, and the man doesn't question it. He thinks she's cute, carrying her brother's camera.
She watches Frank lay out checks on the floor of their hotel room as she eats an ice-cream sundae. She knows that what he does is not right, but she doesn't care. She likes this better than Jack and Paula. Frankie buys her nice dresses and lets her call him brother, if she wants. She likes to play with the plastic planes after he's taken off the stickers, and he even bought her some paints to paint some of them to make them look different. She likes it.
When the attendant asks if he's her deadhead, he makes sure there's a place for Susan on the plane. "Of course," she says. There are usually a few extra seats, and family flies free. She watches as he dangles a glinting pendant from his fingers. "Is this yours? It must have slipped right off your neck." The stewardesses are all enamored with her, with her pretty dark hair and quiet manners; and when he talks about her none of his pride and fondness is pretend. She starts to not be so shy.
Whenever Frank has a girl, he gets two hotel rooms. He's not going to just put Susan out for a few hours while he's having fun with whatever stewardess has caught his eye. Susan knows what he's doing, she's not stupid. She doesn't always stay in the room. Sometimes she goes to an open-late restaurant and charms a free sundae from the waitresses, before going back to the room and looking out the window at streetlights and neon glinting in the dark.
Agent Carl Hanratty bursts through the door to their hotel room yelling, and she drops the painted plane she was playing with, her eyes wide. She doesn't panic, though. Frankie doesn't burst through the door, so she must not be in danger. Carl finally lowers his gun when he says he's Secret Service, but asks for ID. After yelling that he doesn't want LAPD on his scene, he gestures to her. "She was with him. I was going to take her out to the car with some of the evidence, I-I don't want to leave her up here alone, and my partner is taking the old man. Hey, do you mind staying here while I do that? I don't want the maid to clean up the crime scene." The minute they're out of hearing, they start running. When they hear the agent yelling from the window, he laughs and she giggles. They don't stop the entire time they're running.
He calls at Christmas, apologizing. He really means it. Carl asks why he's calling. "You don't have anyone else besides that little girl, do you?" He laughs long after the con-man hangs up, though he feels a certain ache in his chest as he does it, one in between sympathy and pity and that feeling he has when Grace doesn't have time to see him.
Frankie stops being an airline pilot and starts being a doctor. She watches him put the glinting gold sticker on the counterfeit diploma. When she meets Brenda the nurse smiles at her, her braces glinting. She doesn't like Brenda. She knows that it's not fair, because she has no reason she can think of besides that she wants to keep her brother to herself. She can't bring herself to care. She doesn't tell Frankie.
When Frankie tells her he's marrying Brenda she says okay. He's determined to figure out why her eyes look like they did in New Rochelle. Later that night he rocks her, having told her that she will always come first, before Brenda. Her eyes glint with leftover tears and she thinks that this might not be so bad. But she still doesn't like Brenda.
Brenda's parents don't know what to make of the boy wanting to marry their daughter. They know even less about the quiet girl he brought with him. She answers their questions even more vaguely than Frank. She's quiet, though, and unobtrusive. She watches. She watches Frankie study for the bar and she watches the odd people that live in the house.
At the engagement party, Frankie drags her to the top bedroom with Brenda. She watches the moonlight glint off their faces and knows that this is not going to work out. After escaping out the window she tells Frankie. He gives Brenda the benefit of the doubt. Susan doesn't like the glints in his eye on the way to France. When they get there she hugs him and he breaks down. He loved her.
He hasn't been doing well since Brenda betrayed him. He told her all about his dad. She thinks she'd like to meet him. She didn't get to see him the couple of times that Frankie did. Frankie misses his parents, especially his dad. For the first time in a long time, Susan feels afraid.
Seven months later, Susan knows French. She refuses to go to bed until he does in a vain attempt to get him to act healthier. Agent Carl Hanratty comes in, and she knows it's all over. She watches Frankie's face, not quite able to hear him over the printers, except sometimes. And she watches Carl's face and thinks that he really wants to help him. Then they walk outside and it all goes to hell. The French police arrive and point guns at them and take Frankie. Before he's taken she hears him yell, "Take care of my sister, please!" There's fear in Frankie's gaze and panic in Carl's and she knows. She knows Carl wants to help Frankie and knows that her brother is not going to be okay. After Frankie is taken away, Carl wraps an arm around her and it feels nice even while she's breaking. A tear glints on her cheek.
He takes her back to Jack and Paula, and they treat her well enough, if a little distantly. Carl shows up every once in a while to check up on her. She thinks it may be because she kept calling Jack and Paula by their names, but she can't bring herself to care. As far as she's concerned, Paula isn't her mother, and she likes Carl better than Jack anyway.
A year later Carl shows up and tells her that he's bringing her brother back to the United States. She's startled when he shows up in front of the window she's gazing from. His hair's long and he's not dressed for this weather. "My dad?" She presses her hand against the glass and shakes her head. He just sort of crumples without moving at all and flashing lights glint off the windows. He goes quietly and she wishes that Carl was with her. Jack and Paula haven't even looked out the window.
Carl keeps visiting, and brings her to Frankie every once in a while. Jack and Paula tried to keep her from seeing him, but after some words from Carl they don't say anything else about it. Frankie looks like she felt two years ago, before he took her with him. Until Carl picked her up and drove all night so she could watch as Frankie comes alive again figuring out how a check was forged. When they walk out of there, she giggles.
Frankie is at the FBI building looking at a new type of check when Carl tells him that he's arranging it so that Susan won't have to stay at Jack and Paula's anymore, because the way Jack used to treat her could be construed as neglect and they don't really want her anyway. Frankie can't adopt her, because he's on parole; but Carl can. Frankie's so happy; he smiles, and his eyes glint suspiciously.
Only a couple of days later, Susan walks right into the FBI building like she's meant to be there and hefts herself onto Frankie's desk. After some asking in vain about how she got there, much less in the building, Carl calls her school and Frankie hugs her and starts talking with her. She said she was on a field trip. An hour later, her teacher comes in looking flustered and asking her how she got here. Susan immediately looks innocent and contrite. "Well, I saw a necklace on the sidewalk and went to pick it up. When I turned around, everyone was gone. I knew where my brother worked, so I came here." She glanced up through her lashes. "By the way, is this yours?" She dangles a glinting pendant from her fingers. The teacher replied that it was. "It was the one I found on the sidewalk. It must've slipped right off your neck."