I totally agree with Milena. The love story between Marcella and Cal isn't the main aspect in the novel. I could imagine that the author just wanted to add an other fact than the conflict between Catholics and Protestans, to create the novel more diversified and interesting for everyone. The priciple "love story" almost works in books, movies etc., therefore the author connected the main conflict with this love story. But for me it is/was allways clear that the love story isn't the main theme of the book, so it can't called a love story. The novel focuses on the conflict between Catholics and Protestans and also on Cal's feelings and thoughts about the IRA (like Milena said), the love story maybe express how Cal become more self-confident and how/why he changed, so it supportes the main fact in some parts but it isn't really necessary for the main story.

Of course it would be a very difficult and hard situation for Marcella and also for Cal, who is arrested and is so sorry about his past. But Lennard you said:" I mean, she's older than him, has already a daughter and her family wouldn't be ok with the fact that she loves or is in a partnership with the guy who supported the IRA or killed her husband." I don't agree with you, because I think that Marcella doesn't like Robert's family, the farm where she lives and her whole life in this town. She hasn't friends or any social contacts in this city. So I think, Cal is a very special person for her. He brings fresh breath in her live ("Frischen Wind in ihr Leben bringen"), he is younger, but in my opinion it doesn't matter, because this is the special thing. Cal "fascinates" Marcella because of his age and his juvenileness, so the age difference isn't the problem. Besides I want to say that "the guy who supported the IRA" is a very strong statement. Of course he supported Crilly and Skeffington, because of his shyness and missing self-confidence. But in the course of time Cal changed, he becomes more self-confident and adult. In my view he will convince Marcella that he didn't join the IRA as a confident voluntary and that he is really sorry about what he had done. Maybe Marcella will need time to think about it, but at the end she will decide for Cal and a future with him. In my opinion they will live together in an other city, away from the past and also away from Robert's family. Maybe my ideas and thoughts are to optimistic and romantic, but I'am really sure that Cal and Marcella have a chance of a life together. ;)

I think it doesn't matter that we can't change our names, because I have no problem to say my opinion and my thoughts. The topic you chose is good and I think also very important, but I guess we just have to discuss one topic and come to a conclusion? So we have enough time till the 20th of March. ;) Anyway I want to express my thoughts about this question.
In my opinion the story wouldn't change dramatically, because in the book it becomes clear that Marcella didn't love her husband anymore. When Cal asked her if she liked him, she answered:"Recently-not much." (p.124) Marcella talks about his lies, his affairs, his drinking and that he spent al lot of money. (p.124) So I think they didn't love each other, but Marcella stayed by Robert because it was comfortable and they have a daughter, so she didn't make the step to go away. The death of Robert changed her life and I think she was a little bit glad that her "old life" came to an end. Certainly she was hurt an sad about his death, because Robert was the man she really loved and the father of her daughter. If Cal tells Marcella what he had done, she would be surprised and shocked I think, because it would be a very difficult and weird situation for her. But in my opinion that wouldn't change anything about her feelings for Cal. Maybe she disrupts the contact for a few days to think about what he told her, but she never would "leave" Cal. At page 101 she says that Cal is good for her, he makes her feel younger. So my final statement is that the story wouldn't change dramatically, because there is something between Cal and Marcella that is so strong that Marcella could't interrupt the contact.