I think most of the characters in this show have rather complicated personalities, and the one I struggled most to understand certainly was Marla. It all made sense until… well, she turned out in that episode to be a tomorrow person as well.

"I've told John he can stay here for as long as he wants." It's far from being a request, far from a friendly tone but Marla doesn't argue; for Stephen's sake as well as for the boy's sitting down drowsily on the couch.
Boy. Man. He certainly is older than Stephen, but at the same time he seems younger; less settled, less confident than her son. She doesn't understand how Stephen manages to find strength in the powers that can cost him his life, but he does and she knows he owes it, in parts, to their guest. Marla smiles sadly as she remembers. Giving good advice to others is so much easier than take up that same advice for oneself. She knows.
God, she knows.

"John Young?" She asks out the name, a common tactic she's learnt at the hospital. You learn a lot from a person's reaction to his name.
"Mrs. Jameson?" He's up again at once, his head cocked so he doesn't have to look down at her. "I hope I don't cause you any inconvenience, I…" his voice trails off as she can't bite back a bitter smile. "Inconvenience" is a nice little word for all that happened today.
The attempted assassination of Astrid and her whole family. The disclosure of her identity to the world, and to Stephen. Luca's grades don't make things easier – especially because she knows he could do better if he only showed some interest in anything. Which reminds her that in the past months she has not have the time to show much interest in him.
She's done everything to hide the truth from her sons, and only now she realizes she's been blind as well.

John misinterprets her silence. "I'll better go now" he says, almost gently, "say thanks to Stephen from me. I'm sorry."
"Wait!" She forces herself to smile. "It's… this is not about you. You helped my son survive, you are his friend… you are welcome."
John smiles shortly. "I've not exactly always been his friend. And he's saved my life, too, so… there's really nothing owed here."
"That's not what I've meant. Please." She motions for the couch again and hesitantly he comes back and sits down again, his glance restlessly wandering around. She waits until he finally dares to look at her. "You are welcome to stay as long as you want to. Stephen made this offer to you and I am happy to affirm it. Understood?" She notices his lingering hesitation as he nods, the insecurity in his eyes.
His eyes… when John finally nods, she almost jerks away. It is true. She's always believed it, despite or because of Jed constantly denying it.

"Thank you." Finally, the smile reaches John's eyes, lighting up his face, and it becomes even clearer. However Jed found him, why ever he didn't tell him… John Young is his son. No wonder Stephen hasn't seen it until now, Marla's sure he hasn't seen Jedikiah smiling. He rarely does. Truth be told, when Marla started dating Roger she thought Jed was adopted; they seemed so different. And yet they loved each other, so deep that she thought nothing could ever get between them. Wrong at that. But at least she had been true about the six months after her wedding, when Jedikiah seemed both desperate and overjoyed. He never explained why, and after those months, he became the sullen, bitter man he seemed to be now. Less dangerous then, though.
If Marla had known what would become of her brother-in-law, family or not, she would have killed him then.
She could have done it.

"You have the ability to kill, don't you?" She blurts out without thinking, and in without thinking reaches for his shoulder as he backs away –

A girl running through rows of corn, behind her the smoke of a burning farm. She didn't mean to set it aflame, she didn't, she was just so angry at her dad for not letting her go to Hugh's party, and then suddenly the chimney seemed to explode, there were logs flying around everywhere, one hitting dad straight in the face and then – she runs faster, they can't find her, they can't; she's heard stories of the people they capture, they always get tortured and die – she runs until she reaches the street. There's a car waiting, a black car, and before she can turn around the door opens and Hugh's father steps out, followed quickly by his son; and the girl feels safe, safe at least

John pulls back. "The founder" he gasps, recognizing the face, forty years younger but even then determined to have everything according to his wished. Marla can only nod, shaking with both shock and shame as more memories of that time threaten to swallow her. "I understood too late that his father was the one capturing people like us", she says slowly, as if that could explain everything she did.
Gently, John puts his arm around her shoulders, careful to shield his mind from her. "I'm sorry. For all that happened."
He must have a hundred questions burning on his tongue and she knows she has to answer most of them; they need every advantage over the founder and his methods that they can get; but he doesn't ask her right now and for that she is grateful.
Again she wonders who his mother is. She must have been both beautiful and intelligent to attract Jedikiah, and ambitious or he wouldn't have taken her serious. On the other hand, she clearly has given her son the gift of compassion, something Jedikiah even on his good days totally lacks.

"They made me a warrior as well" she whispers after a while, "they made me a killer as well." She smiles tiredly as John pulls back again. "Stephen didn't tell me. I saw it in your eyes. I saw you in my eyes." Which is a harsh thing to say, and at once she wishes she could take it back. But she can't.
None of the things she did today.

"Would you?" John looks at her, more curiously than judgingly, as he poses the question in her mind. It seems almost like a play, a game she hasn't played for far too long. She kept her powers hidden from Roger, hidden from herself after she managed to escape the Bathory's recruiting base. Or was she set free? A testing object, put into society for Hugh's father to watch.
If she hadn't been so eager to hide her true self, would she have recognized Roger's powers earlier?
When she did, it was too late. He had already made his decision to leave, and Marla didn't argue. Their powers have to be controlled and smothered, for the sake of the family. When Roger showed he wasn't able to do it, she let him go. For the sake of the family, for Stephen and Luca… how could she have known Stephen would be like her? Like them? She's forbidden herself the thought it was heritable. Her sons, her beautiful sons, couldn't be born to destroy humanity.
As Bathory made her believe she was born to do. As she has done, until…

"Marla." He doesn't touch her again, but something in his voice calms her down enough to closes the doors of her past again. No matter what John got through, it didn't harden him, and she understands now why both Jedikiah and Stephen love him – despite the fact that neither of them will ever put it in those words.
She sends the feeling out to him and he smiles, embarrassed but thankful, before she thinks about the question again.

Would she take back any of the things she did today? She saved Astrid. She stood up next to her son, against Ultra. Against who she was once, and what she then chose to fight against in her own way. By becoming a nurse, by saving people.

"No." This time her smile is genuine, and she feels a ton of weight fall off her shoulders and her heart. "No, I think it was about time." John smiles a little.
"Alright" she says loud, "I'll better leave you sleeping. I guess we'll have to discuss matters of war tomorrow." She shakes her head at herself as she gets up, sensing John's wondering behind her. Again, however, he doesn't ask any questions.

"Don't tell Stephen what you saw" she begs when she leaves, "I know I owe him explanations but…"
"You don't owe him anything", John sends back, both determined and tired. "Look, I don't know much about mothers, but I know you love him, and you've protected him all his life. You've built him a home, and you will not let him get hurt. I think that is all anyone can ask for."
She feels the longing in his mind, the deep ache for what he sees in this house, in these people. But before she can find anything consoling to say, he continues, "I know a thing or two about being made a monster, though. If there was no forgiveness for you, how could there be for me? You were forced to do one thing, then you made your own decision. That's all that matters."
"Thank you." She finds a small laughter in her mind. "Ever tried to forgive yourself?"
The silence that follows proves true what she's seen at once, and an instinct stronger even than the one to hide her powers cries out: the instinct of a mother.
"Do it", she urges, sending him pictures of Stephen, of Astrid. "You saved them. And countless more. For those two alone, I will never stop being grateful to you. I don't care what you did, I care for who you are now. Remember, that's all that matters."

John tenses as Marla reaches out for him for the last time, her whole being filled with affection. It is all he can do to stay quiet as she bids him good night and leaves, finally, both the room and his mind.
He crouches down as soon as he's alone, memories washing through him, drowning him.
Cara. Who is the only person he trusts – probably Russell, too, and sometimes Stephen – and who exiled him from home.

And, even more painful right now, Roger. Stephen's and Luca's father. Marla's husband, whom she lost, apparently without ever explaining herself to him.
Roger. A good man, a beloved and loving and brave man.

Whom John killed.
And that, neither Marla nor he himself will ever be able to forgive.