This is obviously based on Holby Sin City. I actually didn't enjoy the episode that much when I watched it, but I woke up with this idea in my head. It wouldn't go away so I'm afraid I'm inflicting it on you.

Cal awoke with the impression he wasn't alone.

The thought made him smile. He liked waking up to find he wasn't alone. It was usually a sign of a great night – whether he could remember it or not.

Smiling, he reached across the bed to where he expected the girl to be, but he felt nothing and could smell nothing to suggest a girl had ever been there. Confused, Cal rolled over onto his other side, but he was right on the edge of the bed and there wasn't space for anyone else.

Then a voice said his name. "Cal?"

It was dark. Cal couldn't see who was standing there: only that there was a dark figure with a hat on, but he knew who it was. He reached for the light switch and looked at the doorway again, only to gasp at the state of his brother. He was dripping wet and shivering and he'd forgotten to change out of his scrubs. His face was wet too: at least some of it was probably rainwater, but Ethan's little gasps for breath sounded so much like sobs, Cal guessed there were tears on his face too.

At first Cal was too stunned to do anything. All he could do was stare at his little brother in horror and wondered what could have happened. Then the doctor part of his brain woke up and told him Ethan needed to get out of his wet things.

And by the time he'd reached Ethan's side, the caring big brother part of his brain had woken up too. He put his arms around Ethan and held him tightly. "What happened, Nibbles? It's okay. It's going to be okay."

Ethan's only answer was to burst into proper sobs. He was shaking hard and Cal didn't think it was just that he was shivering with cold. Something had happened. Something terrible.

Cal felt panic rising inside him, but he knew he couldn't let it take hold. He stroked Ethan's back and told him again that everything would be okay, even though he was terrified it wasn't true. Then he felt the rain from Ethan's coat seeping through his pyjamas and stepped away from him, though he kept his hands on Ethan's shoulders.

"Ethan, listen to me. I know you're upset and I'm going to help you, but first you need to take your wet clothes off or you'll catch pneumonia. I know you probably don't care at the moment. I know you probably think you couldn't feel any worse if you did catch pneumonia, but it will make you feel worse and I care even if you don't." Cal heard his voice shake slightly; he took a steadying breath and continued. "Besides, if you get pneumonia, I'll have to take you to the ED and I don't think you want that right now."

He wasn't sure if Ethan had heard. He was still crying and shivering and he looked horribly pale too, Cal realised. He took the hat carefully from Ethan's head and then put it out of the way on the floor. Then he gently undid his coat and put that on the floor too. He touched Ethan's arms and discovered his scrub top was also wet, so he removed both that and the t-shirt he wore underneath it. Ethan's trousers were wetter still.

"Okay: come and sit on the bed for a minute," said Cal. He helped Ethan to sit down, wrapped him in his duvet, then knelt and removed Ethan's shoes and socks as carefully as he could. Ethan was still crying and Cal doubted he was capable of doing it himself. Cal rubbed Ethan's feet dry with a random item of clothing he'd found on the floor. It probably wasn't ideal, but at least he could reach it without letting go of Ethan.

Letting go of Ethan didn't seem to be advisable at the moment, but Cal was only too aware he'd have to leave him soon.

"Ethan, I need you to take your trousers off for me: okay?" said Cal. There was no answer from Ethan. Just more tears. A sudden, horrifying thought entered Cal's head and he stood up, grasping at Ethan's shoulders. "Oh God, Ethan, did someone hurt you? Attack you?" Still no reply. Cal felt his legs shaking and sat beside Ethan. "Ethan, I know you don't want to talk and that's fine, but please nod or shake your head. Did someone attack you?"

Ethan slowly moved his head from side to side.

"Thank God!" said Cal emotionally, hugging Ethan again, but in a moment, he was back in control. "Ethan, you do need to take your trousers off. If you can't do it yourself, I'll have to do it for you. But it's okay. It's not like I haven't done it before and I'm a doctor so you can trust me."

Ethan continued sobbing, but he managed to nod his head.

"Good!" said Cal, even though it wasn't. Nothing about what was happening was good, though at least Ethan had come to him. He'd known Cal would look after him. Despite everything.

Cal made sure Ethan's legs were covered by the duvet. It was a double one and gave Ethan some illusion of privacy. It wasn't necessary when Cal was his brother, but he knew Ethan was feeling vulnerable and he didn't want to do anything that might increase the feeling. He carefully removed Ethan's trousers and moved away, but Ethan grabbed at his hand, his distress clearly increasing.

"Okay: you can come with me," said Cal softly. He helped Ethan to his feet and held his hand as they walked the few steps to Cal's chest of drawers. His clothes were shoved randomly into any old drawer, but he managed to find a pair of pyjama bottoms which he knew were clean because they would be on the floor if they weren't. "Here you are, Ethan." He knelt down in front of him. "Can you lift your foot up for me? That's right. And your other foot? There." Once the pyjama bottoms were on, Cal gave him a hug. "Well done. You're doing really well. Now let's just sit here for a bit."

Ethan didn't argue. Cal put his arms around Ethan. He rocked him and stroked his hair and told him everything was going to be okay, but he felt so helpless. He didn't seem to be making Ethan feel better and he still had no idea what had happened.

"Listen, Ethan: I know you don't want to be left on your own, but I need to go and make you some tea," said Cal. "That should help you to feel calmer and warm you up a bit. Will you be okay if I leave you for just a few minutes?"

Ethan continued to cry, but then he nodded.

"I won't be long," said Cal. He gave Ethan a tissue and another hug. "If you need anything, just call me. Or come and find me." He hesitated, realising Ethan probably wouldn't call if he was struggling to speak and he might not have the strength to walk as far as the kitchen. He looked despairingly around his room. He knew he had a football rattle somewhere, but it could be anywhere. With sudden inspiration, he grabbed his alarm clock and set the alarm to the current time. "Ethan, if you need me, just press the switch to turn the alarm on and I'll come and find you."

Cal went to the kitchen. His heart was pounding and he realised how terrified he was. Ethan had said he hadn't been attacked and Cal was relieved to hear it, but something had obviously happened to him. What had he been doing out in the rain anyway? It couldn't have been any kind of emergency where they'd needed a doctor on-site. Ethan wasn't wearing the right clothes. It must have been something that had taken place outside the hospital building, somewhere where there was no protection from the rain, but presumably still on the premises.

But there was so much more to the story than that. Cal was sure it couldn't be a simple case of losing the patient. Not unless he'd known the patient personally – but if that were the case, he shouldn't have been treating them. Perhaps he'd stood outside and watched and got wet, but Cal was sure someone would have made him go inside.

And if Ethan had known the patient, who could it have been? Who could mean this much to Ethan? It obviously wasn't Cal, though Cal had wondered lately if he meant anything to Ethan at all. Honey? Had she come back to see Ethan or perhaps Noel and met with some accident? Or was it Lily? She was obviously trying to get her hooks into Ethan, and Ethan had been quite into Lily until Honey had started working at the hospital.

Cal gave a small, emotionless smile. That was the thing about Ethan. You could count the number of girls he'd been interested in on one hand. Recently, there had only been two.

Though there had been that patient. The beautiful, dark-haired femme fatale. Cal hadn't seen her for a while and he wasn't aware that Ethan had either, but Ethan had certainly liked her. He'd even started spouting poetic rubbish to her in the middle of the ED.

Had she broken Ethan's heart?

That actually seemed more likely than anything. A broken-hearted Ethan might possibly forget to get changed out of his scrubs and then go for a walk in a thunderstorm. You couldn't think straight when you had a broken heart. It filled your whole mind and there was barely space for the little things like remembering to change your clothes and making sure the weather was suitable for going for a walk.

Even that didn't quite make sense though. Ethan's clothes had been damp underneath the coat too. And was that coat even Ethan's? Cal didn't remember seeing it before, but he'd never approved of Ethan's dress sense and always tried not to look too closely. And going for a walk in the rain was one thing, but doing it in the middle of the night? Cal could imagine doing it himself, but he was sure that even a heartbroken, rejected Ethan would have more sense.

Cal put several generous spoonfuls of sugar into Ethan's cup and carried it back to his room. Ethan, to his relief, seemed slightly calmer. He'd taken his glasses off and was drying his tears, though he still looked upset.

"Here you are," said Cal. "Be careful: it's hot."

Ethan took the cup from Cal and had a cautious sip. His face twisted with disgust.

"Yeah, I know it's got too much sugar in it, but you've had a shock," said Cal. He sat beside Ethan and put his arm around him. "Go on. It'll make you feel better."

Ethan had some more. Then his face went even paler and threw up all over his pyjamas.

Or rather Cal's pyjamas.

Ethan dropped his head.

"It's all right. Don't worry about it." Cal took the tea away from Ethan and gave him a hug. "I probably did go overboard with the sugar. It wasn't your fault and it's not like you could have told me you weren't feeling well." A thought occurred to him. He'd assumed Ethan was pale because of some kind of distressing incident, but perhaps he was actually ill. He could be delirious or something. That would explain his strange behaviour. "Ethan, can you look at me for a minute?"

Ethan turned his head towards Cal. Cal hadn't seen his eyes before. Not properly. Only through his steamed-up glasses. But they were dilated; unfocused. And not just squinting because he didn't have his glasses on. He just wasn't looking at Cal at all.

Cal was trembling, but he knew he had to ask. "Ethan, have you taken anything? Like drugs?"

Ethan's eyes filled with tears again and he nodded.

Cal couldn't speak.

A drug addict. His little brother. And Cal hadn't even realised. Too wrapped up in his own problems as usual.

Cal was tempted to throw himself down on his bed and howl even more loudly than Ethan had done, but that wouldn't help anyone. "Right. We need to go back to the ED." He found Ethan some more pyjamas. "Put these on. I'll drive you: it'll be quicker than calling an ambulance and I'll be able to treat you if you get worse. We'll take a bucket in case you're sick again. Okay? Can you get changed for me?"

Ethan nodded. Cal went off to find him a bucket and a dry coat. He returned, half-expecting Ethan not to have got changed, but he'd done it. He'd put his shoes on too. He sat, staring down into his lap, not crying anymore.

Perhaps all he'd wanted was for Cal to guess.

Cal sat beside him and gave him a hug. "I'm proud of you, Ethan. It took guts to tell me the truth."

Ethan looked startled. Cal guessed the wide eyes were an effect of the drugs he'd taken.

The drugs his little brother had taken.

But there was no time for Cal to let himself be upset. "Come on: we'd better go. Can you stand up?"

He helped Ethan to stand. He helped him out of the flat and into the car.

And all the time, he was hoping and praying that there was another explanation for this. That Ethan wasn't a drug addict. That he'd taken the drugs accidentally.

It didn't occur to Cal that the truth might – in some ways – be even worse.