Mary looked up from where she was pouring herself a cup of tea as Tom came into the library, her face breaking into a big smile.

'Hello, you. How was your day? Did you hire an apprentice?' Her smile faded as she saw the bandage on his hand. 'Goodness! What have you done to your hand?'

Tom hurried over to her. 'Where is everyone?'

'Mama and Papa are visiting Granny. Why?'

'Is Henry back yet?'

'No, not yet. Why?'

'He came to the dealership this afternoon when he got back from Birmingham.'

'Right. So, he'll be home soon then,' Mary said, any trace of a smile disappearing.

'Yes, I suspect he will. I left before him, but I wouldn't be surprised if he were hot on my heels. I wondered if he might have beaten me back because I stopped off to see Mrs Hughes.'

'Did you? Why?'

'I needed her to act as Florence Nightingale and bandage my hand,' he said, wincing slightly as Mary picked up his hand, examining it in concern.

'What did you do to it?' she asked, only to be stopped in her questioning by Henry barging through the door.

'Ah, right, so you couldn't resist coming straight to her to make trouble then? I should have bloody well known you would,' he snapped at Tom when he saw him standing next to Mary. He flicked his eyes angrily over to his wife. 'I suppose he's already told you all about it then, has he?'

'Told me about what?' Mary asked, staring in astonishment at his cut and swollen lip. 'What on earth happened to you?'

Henry faltered, realising he'd jumped the gun. 'Er… I… I… well, it's…'

'I hit him,' Tom said, glaring at Henry before turning to face Mary.

She gawped at him. 'You hit him?'

'Yes. Punched him in the mouth.' Tom cast another angry look at Henry. 'Are you going to tell her why or shall I?'

'Oh, why don't you, Tom?' Henry bit out, furious at having been forced into this position. 'I know you're itching to tell her. Far be it from me to deny you the pleasure.'

'Actually, I think it would be better coming from you,' Tom replied, determined not to let him off the hook.

Mary looked back and forth between them as they glared at each other in the furious silence that followed.

'Will one of you just tell me what's going on?' she finally demanded.

Henry clenched his jaw, pressing his lips tightly together in anger.

'Henry?' Mary said expectantly, waiting for him to tell her what this was all about.

'Fine. I'll tell you. But it's nothing. It doesn't mean anything. Tom's making a mountain out of a molehill.'

'What doesn't mean anything?'

'I'm guilty of having had a little dalliance,' Henry said, off-handedly.

Mary frowned at him. 'A dalliance?'

'Yes.'

Mary stared at him, conflicting emotions swelling inside her as she realised what he was saying. 'You mean you've been having an affair?'

Henry glared at Tom then switched his attention back to Mary, trying to look contrite. 'Well, I wouldn't characterise it as an affair as such.'

Tom snorted in derision. Mary glanced at him then focused back on Henry. 'Then what would you call it?'

'A dalliance,' he repeated. 'No more than that. It doesn't mean anything, darling. I love you, you know that.'

'You love me? The fact that you've been sleeping with another woman would seem to indicate otherwise,' Mary said, her voice like ice. 'Who is she? Is it someone I know?'

'She's no-one. She's not important. She doesn't matter,' Henry replied, dismissively. 'She's not even worth thinking about.'

'Really? And yet you thought enough about her to take her to bed.'

'She caught me at a weak moment, that's all,' Henry said, looking beseechingly at his wife.

'Liar!' Tom exploded from beside Mary.

Without taking her eyes off Henry, Mary reached out and put her hand on Tom's arm, silently warning him to calm down.

'Oh, so it only happened the once, did it?' she enquired, her voice calm and steady.

Henry shifted his weight awkwardly from one foot to the other. 'Er, well, no, it was more than once.'

Mary arched an elegant eyebrow. 'Twice?'

'No, more than that,' Henry said, shortly.

'Ah, right, so she caught you in a series of weak moments, did she? How fortunate for her. What impeccable timing she appears to have. And when, pray, was the first weak moment?' Mary asked, keeping her voice calm, sweet almost.

For the first time, Henry looked downright uncomfortable.

'When, Henry?' Mary asked in a clipped voice.

'Just before Caroline was born,' he mumbled, at least having the grace to look shamefaced.

Tom glared at him, rocking forward, desperate to punch him again, only to be stayed by Mary's hand on his arm once more.

Colour flooded Mary's cheeks as she looked at her husband with contempt. 'You took another woman to bed while I was pregnant with our daughter?'

Henry was silent, not meeting Mary's unwavering gaze.

'Do you have nothing to say?' she asked him, coolly.

'It was simply a physical thing, Mary. You were too uncomfortable to have relations and I needed a release. You know how I get if I don't have a release,' Henry blustered, a pleading note in his voice. 'That's all it was, I swear.'

'And yet, by your own admission, you have "dallied" with her more than once. Is it over or is she still helping you find "a release"?' Mary asked, disparagingly.

Henry shot a furious glare at Tom.

'Don't look at him,' Mary said, forcefully. 'Look at me. I'm the one you've been cheating on. Answer the question. Are you still sleeping with this woman?'

Henry met her gaze, mutinously. 'Yes.'

Mary stared at him, pursing her lips. 'Caroline had her first birthday last month.'

Henry pressed his lips tightly together, his mouth a thin, angry line, mute as Mary thought it all through.

'So, you've been sleeping with her for over a year.'

Henry still said nothing, but his face flushed with colour.

'You've been sleeping with me too over this last year. How many 'releases' do you require in a week to maintain your equilibrium, Henry?'

'Not recently, I haven't,' Henry flung at her, petulantly. 'You've been turning away from me, claiming you have a headache or your monthlies more often than not lately. You refused me on Friday night if you remember.'

'Ah, so it's my fault is it, your sexual incontinence?' Mary snapped, shooting her hand out to grab Tom's arm once more as he rocked forward again in fury at Henry's mention of Friday night. 'First because I was too heavily pregnant to accommodate your urges and then because I wasn't in the mood? You are blameless in all this, are you?'

'Of course not, but you have to admit, if you turn away from me in the bedroom, it's hardly surprising that I should have to seek relief elsewhere,' Henry retorted.

'But I was not turning away from you for most of the time you have been enjoying this "dalliance" as you so euphemistically refer to it,' Mary pointed out. 'So, what is your excuse for the rest of the time?'

Henry stared at her, gritting his teeth as he cast around for an answer. Eventually, he settled on glaring at Tom. 'You can go now, Branson. This is nothing to do with you. It is between me and my wife.'

'Stay where you are, Tom,' Mary said crisply, tightening her grip on Tom's arm even though she knew he had no intention of going anywhere.

'This is none of his business!' Henry snapped.

'And yet I want him to stay because I do not wish to be alone with you.'

Henry stared at her in shock. 'You can't possibly think I would hurt you, Mary.'

'I wouldn't presume to know what you would or wouldn't do, Henry, because it appears I do not know you in the slightest,' Mary replied, calmly. 'And you should not assume that it was my safety I was concerned about. There is every chance that I might hurt you at the moment.'

Henry huffed out a short laugh at that before seeing the icy resolve in Mary's eyes and reconsidering the truth of her statement.

'I will not discuss this with him here,' he said, flatly.

'You will do as I wish. I am the injured party here and if I want Tom to stay, he will stay.'

'He's in love with you, Mary!' Henry cried. 'Did you know that?'

Mary flashed a quick glance at Tom, noting the furious look he gave Henry. 'Don't be ridiculous. Of course, he's not.'

'He is! And I know he's been trying to get you to sleep with him!' Henry exclaimed.

Mary's mouth dropped into a perfect O at that. She gaped at her husband, not quite sure she'd heard him correctly. 'I beg your pardon?'

'I know you had a falling out about it. Those weeks where you were barely speaking to each other and you were going out of your way to avoid being around each other. Did he make overtures? Try to get you into bed?'

Mary couldn't help it; she laughed in Henry's face. 'No, he did not. What on earth put that idea in your head?'

Henry flicked his gaze between them, looking uncertain for the first time. 'I… I accused him of it earlier – of trying to get into your knickers – and he didn't deny it.'

Mary narrowed her eyes at her husband. 'Probably because it was a baseless accusation, and he has done nothing he needs to deny. May I suggest, Henry, that you do not judge other people by your own standards of behaviour. Unlike you, Tom does not have the morals of an alley cat and has never once tried to get me into bed.'

Henry shook his head in disbelief, shooting a vicious glare at Tom, who simply glared back at him. 'No, I don't believe you. He punched me because he found out about my aff… dalliance. Why would he do that if he's not in love with you?'

'Perhaps because he is my friend and brother-in-law and feels as betrayed by you as I do,' Mary suggested, coolly. 'Besides, it doesn't matter if the whole regiment of the Yorkshire Hussars declared themselves to be in love with me. It is irrelevant to the matter at hand. There is only one person here who has been breaking their marriage vows by sleeping with another person and that is you.'

'Mary, I –' Henry began, only for Mary to raise her hand and silence him.

'No, I will listen to no more of your feeble attempts to justify your behaviour. This marriage is over, Henry. You may stay at Downton tonight, but you will leave tomorrow.'

'No, no, you don't mean that,' Henry said, utterly shocked.

'I do,' Mary said, implacably.

'But you can't! You can't end our marriage just like that!' Henry cried, desperately.

'I can and I have.'

'But I love you!'

'Do you? Because you have a most peculiar way of showing it.'

'Mary, you can't do this. Let's talk about this. You can't just cast me aside like this!'

Mary gazed pitilessly at her husband. 'Did you really think I would roll over and simply let you ride roughshod over me, Henry? I will not put up with your behaviour for one minute more. We will talk about this again, but only to finalise the details of how we will end this marriage.'

'No, no, I don't believe you would do that. You don't want the scandal of a divorce. I know you, Mary,' Henry said, walking forward to try to take her hands.

Mary felt Tom bristling next to her as she snatched her hands away from Henry's grasp. 'I would rather endure a scandal than live with the knowledge that I let you cheat on me and get away with it. My pride would never allow such a thing.'

'Your pride? Do you really think that is the most important thing at stake here? We have a child! What about Caroline? You can't do this to her!' Henry declared, playing what he thought was his trump card.

Mary eyed him coldly. 'Caroline is too young to know what is happening here. But I believe it is important for her to learn when she is older that there is absolutely no reason why she should put up with a faithless man. And I will be glad to be the one to teach her that lesson.'

Henry gawped at her. 'You wouldn't tell her about this?'

'About why I divorced her father? I absolutely would,' Mary said, exuding both determination and calmness. 'As I said, you may stay at Downton tonight, but I expect you to leave tomorrow.'

'And where do you suggest I should go?' Henry bit out, his temper returning.

'That is not my concern. Perhaps your mistress will let you share her bed once again. Or perhaps your aunt will take you in. Quite frankly, Henry, I don't care. But, mark my words, this will be your last night under this roof.'

'And where am I to sleep tonight? I can't think you will welcome me to our bed.'

Mary studied him thoughtfully. 'I will relinquish our bedroom to you tonight, so you can pack your things. I will sleep elsewhere.'

Henry subsided into a furious silence.

Mary gazed at him, waiting for any further argument. When Henry stayed silent, she nodded her head. 'Come on, Tom, let's leave Henry now to consider where he can relocate to.'

'Yes, that's right, off you go with your pet poodle,' Henry snapped, staring daggers at Tom.

Tom opened his mouth to retort, only for Mary to beat him to it.

'My pet poodle, as you call him, gave you a fat lip, Henry. I see no mark on him other than the damage he did to his own hand,' she said, in a voice like ice. 'If I were you, I would bear in mind that Tom has a background of dealing with men much more dangerous than you. Irish Republicans. Black and Tans. Royal assassins. Perhaps you should consider that you got off lightly.'

Henry glared at her, at a loss for a comeback.

Mary stared coolly back at her husband until he looked away. She glanced at Tom and he nodded at her. As they left the library, Mary silently rejoiced at managing to keep her complicated range of emotions to herself throughout the confrontation with Henry. While part of her was ecstatic that Henry himself had handed her the means to end their marriage, another part of her was excruciatingly humiliated to discover her husband had been unfaithful to her for most of their marriage.

For now, though, she needed to set aside that second part of her. At the present moment, she needed to find somewhere discreet to have a council of war with Tom and discover exactly what he knew about Henry's newly revealed affair and work out how she could use that to set about divorcing her feckless, faithless husband.