Although their closeness has been growing for some time now, it all comes to a head when Carly learns that Jason knew Jerry was laundering money for Moreno all along. She feels that Jason should have told her so that she could give Bobbie a heads up and keep her mother from being hurt. She is very upset with Jason and is really tearing into him with a rant when he grabs her and plants a big kiss on her.
Until this time, Carly has been in battle between her heart and her head. Her heart tells her that Jason has feelings for her just as she does for him, but her head reminds her of all them times that he has rebuked her advances, even before she was married to AJ. This time, it was not a matter of her approaching Jason, he actually made a move on her.
This really changes things for Carly as she finally is able to believe that there is a future for her with Jason. Prior to this, she would have been out in the cold if she left AJ to be with Jason. With no viable income on her own, she always knew Jason would provide for her, but the long term was always in question. She knows from experience that if Jason has an interest in a woman (Robin, for instance), the woman is not going to have an interest in Carly! Without the hope of a romantic involvement with Jason, she knows that a battle will ensue if he becomes involved with another woman; a battle that could leave her in the streets. At least with AJ, her future was assured as long as she played the good wife. Now, with the hope of a life with Jason intact, Carly feels she has more bargaining power in her corner. Finally, she feels safe to abandon her Quartermaine financial security and pursue a life with the man she loves. Sarah Brown (Carly) explains, "[The kiss] means that everything that Carly hoped for, longed for, strived for, struggled for and did horrible things for, is maybe coming to fruition, that the object of her desire might actually love her back. And he kissed her. She didn't make him do it. This is a statement to her above all others that she should leave AJ"
Why was Jason so aloof once he began to recognize his feelings for Carly? The biggest reason lies in Michael, who he still considers to be his son, despite legalities and biology. He knows that Michael has been through enormous changes during his formative years and is concerned about him having to adapt to another situation that is bound to be surrounded by stress. He really felt he was doing the right thing in conceding his rights and knows that if he were to tell Carly he loved her, she'd uproot Michael yet again and no doubt become embroiled in a custody battle with AJ. With her history of being in Ferncliff and his work in the mob, there is little chance that they would win custody, which would result in Michael losing both Carly and Jason. By remaining silent, he allows Carly to continue to believe they can never be together and keeps Michael's stability intact while only sacrificing his own happiness. Overcome by emotion at seeing Carly upset at HIM for a change is more than he can handle and he kisses her. Now the truth is out and everyone will have to deal with the consequences.
After the kiss, Carly goes home and tells AJ that she is finished with the dutiful wife routine and wants a divorce/separation. Brown continues, "She just thinks, 'a long as I have Jason, nothing else matters. I'm going to be with my man. I'm going to be happy, I'm going to make Jason happy and Michael's going to be happy because of it." She's knows that AJ probably isn't going to be thrilled with the idea of losing the marriage that is such a playing card for him. Deep inside, she is expecting/hoping that he is going to admit that with the problems they have been having, neither of them is happy and ending their relationship is the best thing for everyone.
She gets quite a surprise when he reacts violently to her suggestion. Brown says, "[AJ] goes a little psycho on Carly. Another part of his personality comes out, which is, 'I will have you at all costs. You are my wife. You're not going anywhere.' .... Then AJ throws in the whole baby card and says, 'Go ahead and leave, but the kid stays here.' So that's the obstacle now." AJ finally backs down and tells Carly to leave whenever she wants, but that Michael will not going with her.
Despite these obstacles, Carly thinks about it and decides that her place is with Jason. She leaves the mansion on Thanksgiving Day, taking time to consider how she should handle the inevitable coming conflict. She knows she has to be with Jason and can't stand being around AJ a minute longer. She knows that even if she tries to make it work with AJ for Michael's sake, AJ will never forgive her for wanting to leave and the tension between his parents will not be good for Michael. How can she have Michael, Jason and the family she has wanted from the beginning? As she contemplates this, she ends up in a place she never thought she'd be.