It's the second part of the story, it takes place after season 2 and before the first episode of season 3.
It's been a week. A wonderful week. They have been out, in clubs and restaurants but that night they've stayed in, at her place.
They're in bed, she is tracing patterns on his chest when Tommy breaks the silence, "I'll be in Birmingham for a few days. We'll have a family meeting. I want you there"
"What part of the family business do you want me to be involved in?"
"Obviously, I don't want you to deal with the daily decisions of our illegal activities."
Grace smiles, "Obviously."
"Polly and Michael run the legal side, accounting, etc…"
"That won't leave much room for me."
"You will have every room you want…"
Tommy straightens up on his elbow to look at her very seriously, caressing her face "Grace, I want to share everything with you."
"Thomas Shelby, are you asking me to marry you?"
A playful smile appears on Tommy's face, " I am not doing it properly."
"No, you're not." She answers with a radiant smile.
Tommy gets up and puts on his trousers, " Get up! Dress up!"
"What? No! I'm fine where I am!"
Tommy is searching his inner pocket,"Get up!"
"It's the middle of the night, I'm in my bed, I won't get up"
Tommy kneels beside the bed, "Fine…"
Grace puts on her negligee and kneels at the edge of the bed.
Tommy presenting a ring, "Grace Burgess, will you marry me?"
"Yes!"
Tommy puts the ring on her finger, they are both arboring huge smiles on their faces.
"Now come back to my bed!"
…
Tommy is looking at the ring on her finger. She is looking at him.
"Now you can be introduced properly at that meeting."
"That won't soften Polly 's wrath"
"I don't care "
She has never seen him so happy, so care free.
" The business needs a foundation, I'll run it. It will give me the opportunity to pursue what I was doing here…It will be good for your business…for your network."
Now he is absolutely beaming.
...
They arrive late, she knows it's on purpose. Tommy wanted to make a big entrance.
Grace is very alert of everyone in the room. Every eye moves on them.
As soon as they recognise her, a wry smile appears on Arthur's and John's faces, an amused one on Finn's. Ada has a reserved expression. Polly is fuming.
Tommy has their full attention when he begins to speak, "I want to introduce you to Grace, even if most of you remember her from a few years back. Grace has accepted to be my wife, she will be a member of this family. From now on, I want you to treat her as such."
He looks at Grace inviting her to speak.
"I know I haven't left the best impression on everyone 's memories. But I can assure you that I'm as devoted to the success of this family as each of you. I promise you that my loyalty lies entirely with the Shelby family." she says confidently.
Polly while getting up and leaving the room whispers loud enough for everyone to hear, "For how long?"
Arthur comes close and takes Grace in an embrace, " welcome to the family, sister. If Tommy is fine with you, so am I."
John lifting his glass, " Welcome to the family"
Ada meets her eyes with a reluctant smile.
Tommy seems satisfied but he is also eager for the meeting to start, " Well, back to business".
After the meeting, she asks Ada for a private moment.
They have met each other twice or thrice since Grace's departure from Birmingham. Their path had crossed in London, Ada was in search of a lawyer who would have been willing to help her with one of the women she was counseling at the library. She was surprised to come face to face with Grace. Grace had apologized for her role in Freddy's arrest and offered her condoleance when Adda had informed her of his passing. Their relationship had been neutral and only business related since.
When she was working for Clive Macmillan, she had been thinking of opening a home for pregnant women and women alone with young children. The house would have a few rooms where women could find a shelter away from the judging eye of society. The idea was to welcome them in a good and warm home and help them start a new life, getting a job and lodging.
During the next few days, she is going to deal with the lawyers of the company to register the foundation. The percentage benefit which will be allowed from the Shelby company to the budget of the foundation will need to be discussed in a later family meeting. But first she needs an ally and a partner for her project.
So she exposes her ideas to Ada, telling her that this will be their first project and that in a couple years they could open an orphanage in Birmingham.
Ada listens attentively and seems interested in these ideas. They decide to meet in a few days in London to start planning for the shelter.