Part 1 of 2
It isn't long after they leave Azkaban that they arrive back at the house. Winky is waiting for them, and she helps Mr Crouch get the trembling figure in his arms upstairs. Crouch doesn't speak to her, but resolutely continues to look straight ahead. He seems stoic and in control, but inside his mind his whirling. What if they'd been seen? What if someone had realised what they'd done? He knows that it can't have happened, as otherwise they wouldn't have gotten this far, but doubts still plague his mind. He still doesn't know if he's done the right thing. He's left his wife, his beloved wife, in that hellhole all for the sake of this pathetic wretch he's dragging up the stairs. Even though he knows it's what she wanted he still can't forgive himself for leaving her there. He's terrified that the moment the cell door closed she realised what she'd let herself in for and changed her mind, and the thought that he'd walked away and left her there alone sickens him. He wants to be with her, to hold her, and find a way to make things better, to fix everything. He'd do anything just to see her face again. But he can't even bring himself to look at the face of the body in his arms, because even though it's Elizabeth's face he knows it's a lie. Everything about his son is a lie. Everything he thought he knew about the boy was just a façade, the result of an ongoing deception that let him get away with doing unforgivable things, and Crouch doesn't know how he's managing to carry the boy up the stairs rather than flinging him down them.
Once they reach the top the first thing to do is clean him up and get rid of the prison grime and dirt. Even as Crouch half carries and half drags the boy to the bathroom he feels the fragile body convulse as the polyjuice transformation begins to reverse. He doesn't want to watch it – he's already seen it one time too many this evening – but he feels the difference as the body he's trying to keep upright collapses to the ground and Crouch hauls him up again. He seems even thinner than before, and Crouch can feel the boy's ribs through his clothes as he leans against him. He doesn't seem able to walk on his own any more and his stick thin legs seem ready to collapse underneath him. Giving up on trying to keep him on his own feet, Crouch picks the boy up and carries him the final few steps to the bathroom, keeping his expression as devoid of emotion as possible.
Once inside Crouch begins to get his son out the clothes he's wearing and he wants to tell Winky to throw them away, but he can't because they're Beth's clothes and he can't bring himself to throw away anything of hers. Not now, not even if it's tainted by this monster he used to call a son. Winky starts to run the bath and steam billows off of the scalding hot water coming from the tap. Crouch continues to undress his son and the boy makes a slight movement as if in protest, but it's so weak and feeble it's hard to tell. Once the bath's ready Crouch lifts his son off of the bathroom floor and lowers him into the water. He feels the boy flinch as his skin touches the hot liquid, but he doesn't stop. Strangely, he almost feels satisfied that the temperature would cause a stinging pain on pale, weak flesh that hasn't seen daylight for months, but then he thinks how upset Beth would be if she knew how cruel he was being and lets a few more quarts of cold water run from the tap.
He picks up a bath sponge and wants to start scrubbing away at the dirt caking his son's body, but he's hesitant. The young Barty Crouch Jr seems almost skeletal, the shape of every bone in his body protruding from beneath the pale, stretched skin. His eyes are closed and his breathing laboured, and in that moment Crouch realises just how easy would be to push his head under the water and let him drown. He doubts he'd even have to hold him there: the boy seems so weak he wouldn't even be able to raise his head above the surface. But the moment the thought enters his head Crouch quickly banishes it with a feeling of self disgust. He could never do that to Beth. Never. But the desire to punish the little bastard for ruining everything refuses to subside.
Even as he starts to scrub away at the dirt and filth he tries to be gentle, but his anger won't let him. He's lost everything: his reputation, his career, and most importantly his wife, and it's all Bartemius Crouch Jr.'s fault. He doesn't want to think about why the boy did what he did; doesn't want to think about how he should maybe share some of the blame, because right now he doesn't care. He wants his son to suffer the way he suffered, and it doesn't matter what Beth would think because Beth isn't here right now and it's all because of him. The rough sponge is unforgiving as it scrubs away at the taut, thin flesh, causing it to burn red where Crouch tries to brutally wash the dirt away, and even when the boy lets out a whimper Crouch doesn't stop. When he begins to clean his son's back he notices the scratch marks covering the boy's shoulders, and he grimaces as he realises they're self inflicted. Even just a few short months in Azkaban were enough to drive him to that, and a sense of horror grips Crouch as he wonders if that's what's going to happen to Beth too. He begins to scrub harshly again at his son's skin, as if by washing away the marks he can wash that thought out of his mind, and he doesn't care when the cuts begin to bleed.
When it comes to washing the boy's hair he finds the violent urge has faded. He can't bring himself to be rough as he starts to rinse the straw coloured locks. Instead he's meticulously gentle – this reminds him far too much of when he used to do this for Elizabeth, when she was too sick and weak to do it herself. Barty's hair is so like hers. It even has that same fine, brittle texture as Beth's had, diminished from its once golden thickness by the disease that was sapping her strength. Crouch can't help but remember back to before Barty's trial, thinking how much healthier he had looked then. He wants to be able to feel some sense of justice in the contrast, but all he feels is a hollow ache.
After he's finished Crouch lifts the thin body out of the now lukewarm water and the boy immediately begins to shiver. Crouch sends Winky to get some pyjamas while he wraps Barty in a towel, but that doesn't do anything to stop the violent shudders wracking the boy's body. Crouch touches his skin where the water has already begun to evaporate off and is shocked by how cold it is. He immediately wraps his son in another towel too, realising that if he didn't Barty could well slip into hypothermia.
When Winky returns she has an old pair of Barty's pyjamas. They were the only pair that had survived: following Barty's arrest Crouch had started trying to burn all of his son's possessions, but Beth had stopped him, screaming that she couldn't bear to lose all traces of him from the house. In the end Crouch had agreed out of love for his wife, but he'd ensured everything Barty owned was locked up in his bedroom out of sight, and Crouch would simply ignore that door every time he passed it in the hallway as if it didn't even exist.
As Crouch begins to try and dress Barty in the button-down pin-stripe pyjamas some of the boy's strength seems to return and he tries to twist away, his arms lashing out uncooperatively. Crouch is still stronger and he manages to force Barty's arms into the pyjama sleeves, but it's so, so hard to be gentle when he just wants to crush the brittle body beneath him and punish him for what he's done. But he knows that he mustn't. It would take hardly any force at all to snap the boy's fragile bones, and Crouch is determined not to hurt him because this is what Beth wanted.
Barty is muttering incoherent noises as Crouch tries to lift him to his feet and he feebly tries to push his father away, but when he refuses to stand Crouch picks him up off the floor and begins to carry him. He's so light it barely takes any effort. Barty gives a wordless shout of protest, but he's too weak to do anything else and he soon gives up trying to move at all, his head lolling against his father's shoulder and his breathing laboured and shallow.
Crouch carries him to his old bedroom; the room he's had since childhood, and the room neither of them have seen in months. Winky has prepared the bed and Crouch gently sets Barty down in it and tucks the blankets up to his chin, like he used to do when Barty was a child. A pang of sentimentality grips him and for the first time that evening he looks properly at his son's face, not trying to avoid it any longer. He's shocked to see the boy's eyes are open slightly, watching him. As he looks into them he feels all the white hot anger from earlier flare up again as he recognizes the expression in them: no gratitude, no remorse; just pure and utter contempt.
Crouch's hand ball into fists and it's so hard to refrain from just killing him there and then. He wouldn't even need magic to do it: the boy was so weak a blow to the head would finish him off.
But he can't do it. He knows he can't, even though preventing himself from lashing out in anger is using up all his self control.
Unable to take it any longer Crouch turns and exits the room, leaving Winky with that bastard he would not call a son and with the boy's look of hate still burning in his mind.