A/N: In response to a really great point brought up by an anonymous reviewer, I know that PD initially wrote Jay as the older brother in the episode where Will was first introduced. However I have done some digging because I came across so much uncertain facts when it came to this subject, as in no wiki site could really decide on whether Jay or Will was the older one. Apparently Med writers ret-conned the older/younger brother thing once Chicago Med started airing and Will got that makeover (notice how his hair was darker when he was first on PD, perhaps to make him look more like Jesse) but Med in the end firmly settled on letting him be his glorious redheaded self and in the process actually made him look older than Jay, so maybe that's one of the reasons they ended up changing it.

I don't think I can post links on ffnet, but this was the tweet from Derek Haas, one of the writers of PD and Med on the subject: "8. namyalmary which Halstead is older? Great question! I think we went with Will being older... did we mess that up in dialogue?"

And this was a tweet from Jesse Lee Soffer: "Oh snap! Halstead has an older brother! #ChicagoPDIsBack #Halstead2X"

So yeah, in the end I decided to go with Will being older and Jay being younger.

Paralytic

The first sign that something was seriously wrong was the fact that Nat had been the one to call him, not Will, but Jay tried not getting a head of himself in concern over that fact alone. Will could just be busy with a patient or tied up somewhere. After all, Nat calling him wasn't anything completely out of the ordinary, she'd called him more than a couple of times in a professional capacity and a handful of times for a slight less than professional reason – meaning she called to complain about Will being an idiot which was a topic that was always of interest to Jay.

So when he asked: "What did Will do now?" the moment he stepped through the hospital doors to find Nat waiting for him at the reception, it was just the natural progression of things.

Jay didn't have to be a skilled detective to deduce that Will had either done something monumentally stupid or something really terrible had happened to him from the seriousness of Nat's expression that didn't falter for even a second when he grinned at her. That was the second most crucial sign.

"Jay," she started, and from the heaviness in her voice alone Jay could feel his heart slowly sinking into his stomach.

"What's wrong? Did something happen?" He started, his grin dropping immediately and the panic slowly taking precedence over his emotions.

"Why don't uh – I'll explain while we walk," she said, reaching over to loop her arm through his, walking him towards one of the closed off treatment rooms at the far end of the ED.

Jay thought that in having a doctor for a brother he'd be more used to hearing all the medical jargon that came out of their mouths, only lord knew how Will could going on and on about stuff without a care no matter how many times Jay rolled his eyes and groaned. He also knew that Nat was simplifying everything for his sake but still very little of the stuff coming out of her mouth was making a lick of sense.

"Hang on," interrupted Jay, raising a hand, trying to keep the dripping skepticism out of his voice, "A tick? You mean like… an actual tick? Like the ones that latch onto dogs?"

Nat let out an involuntary chuckle, seemingly in disbelief over the fact herself. "Yes, a tick. A really big one too. It got on his scalp."

"Christ," said Jay, exaggerating the r slightly as he ran a hand through his hair subconsciously. "Of all the things to get sick of in Chicago," he added just as they came up on the treatment room with the curtains pulled almost completely around the bed, leaving only a small space where he could see Will sitting morosely, staring at an imperceptible spot at the far end of the bed.

"The good news is that it's not permanent and will leave no lasting physical side effects," Nat said with a sigh, which was never a good sign. "However, the bad news is that the illness is still in a progressive stage which means that his condition will get worse before it gets better."

Jay bit his lip. "How worse."

Nat didn't seems like she even wanted to say whatever it was she had to say which was definitely not a good sign. "The paralysis started in his foot and over the last couple of hours has been steadily advancing further up his body. Eventually…" her breath shuddered, "The paralysis will reach his respiratory system and when that happens we will have to intubate."

"Oh man," Jay rubbed his face with the palm of his hands nervously. "Isn't there anything you can do?"

"No. The only thing there is to do is let the toxins run its course which it will… it'll just be a steep fall at first."

Jay sighed, looking back into the treatment room where Will was looking just as nervous and lost as he felt on the inside. He didn't think he'd ever seen his big brother look so – resigned. "Can I…?" he nodded towards Will.

"Of course. Go ahead," said Nat quickly, circling her arm around his elbow and accompanying him to the door.

It must have been a sign of something seriously the matter that Will didn't even notice him standing at the door until he spoke. "Hey, bro," he said, forcing a small smile onto his face that probably looked as disingenuous as it felt on the inside.

"Jay," Will said, almost surprised. Looking up from where he'd been staring blankly at the white sheet covering his legs. Jay noticed the way his fist would clench and unclench where he had them balled on his knees, as if he was trying to massage feeling back into his extremities.

"You really got yourself into a deep one this time, man," said Jay, "A tick, really? If you don't at least develop some super powers after this I'll be very disappointed."

Will forced a small chuckle at his words but immediately lapsed back into silence.

"I'll give you some time. We're prepping a bed up in the ICU, I'll be back to get you when they're ready," said Nat apologetically.

"The ICU?" asked Jay surprised. "You said –"

"It's just protocol, because we know what's to come. Better to be prepared in an environment best equip to give the best care possible," said Nat, trying to lessen the severity of her words to little avail. Jay just sighed.

Will said nothing which was a sign that he was definitely not feeling like himself. Even the doctor side of him was being submissive in that situation and it was a side Jay was honestly not used to.

"It's okay Jay," said Will after a while. "Thanks, Nat," he added immediately after before resuming his silence.

Jay looked up at Nat, watching her as she watched Will sadly before their eyes locked and she left the room without another word.

"Sorry you got dragged in for this," Will said when Jay sidled up by his side, pulling one of the chairs that had been pushed up against the see through divider separating the treatment room from the rest of the department.

"You kidding me, Will?" said Jay with faux offence, "Voight has half the squad doing street patrol today because of some – I don't know, new department policy or some crap like that, so as far as I'm concerned, you're doing me a favour getting me out of that," he said with a lopsided grin that was only half-heartedly reciprocated. "Besides, you're my brother. There's nowhere else I'd rather be."

Those words elicited a more genuine response which Jay returned easily. "Thanks."

"No problem."

Nat and Miss Goodwin returned before long to run one final test and to let them know that a bed was ready for Will upstairs.

"Now just close your eyes and try to relax Will and tell me when you feel something, okay?" said Nat, pulling the blankets half off Will's lower body, the glinting back of a metal pen in her hand. Jay watched as Will leaned back heavily, flinging an arm over his eyes, before reaching out to grasp his free hand lying limp on the mattress beside him. Will latched on immediately.

He followed the movement of Nat's hand as she ran the back of the pen against the bottom of Will's feet, slowly making her way up his shin, past his knees and thigh; pausing slightly to glance over at Miss Goodwin standing passively at the foot of the bed; Will didn't move or make any indication that he felt any of it and Jay could feel his heart dropping into his stomach. With a sigh, Nat continued moving further up Will's leg, past his pelvis and side and just as the back of the metal pen made contact with the lowest rib, he flinched suddenly, letting out an almost choked, "Now."

Nat shared a look with Goodwin and glanced over to lock eyes with him; the grimness in her eyes wasn't encouraging.

"Will," she started.

"It's okay, Nat," Will said, interrupting whatever she was going to say, removing his arm from his eyes and blinking a few times before he looked up at her. "I know."

Jay looked between Nat and Will before his brother finally turned to meet his eyes. "Know what?"

Will sighed, running a hand through his hair nervously before he answered. "The paralysis is progressing quickly. At this rate it won't be long before intubation and artificial ventilation will before necessary," he said; his tone completely robotic like he was trying to get through the words as emotionally detached as he could.

"But it's only temporary," said Nat, trying to for encouragement into her tone and a smile on her face, "It's only until your body completely purges the toxins."

"Yeah, that's easy for you to say from that end of the treatment room," snapped Will sending Nat reeling, looking guilty. Will immediately sobered, reaching out beckoning Nat to take his hand. "I'm sorry, I didn't mean to snap at you like that."

"It's okay, Will. I understand," said Nat, reaching up to cover their intertwined hands with her other, running her thumb against the back of his knuckles. "You'll get through this. We're all here for you, okay?"

"Yeah," said Will without enthusiasm through he tried to force a small smile onto his face for their expense.

"They're ready for you upstairs," came Maggie's voice as she walked into the room, a handful of nurses at her side.

Will inhaled once and let it out slowly through his nose, visibly steeling himself. "Well… I guess it's now or never."

"I'll be here every step of the way," said Jay quickly, getting to his feet as the nurses moved in to transfer the gurney, without letting go of Will's hand for even a second. He could feel the way Will was gripping his hand tight, almost uncomfortably so but he was adamant in keeping the contact. He knew it was the only sign of weakness Will was willing to show and he was ready to take it all onto himself. After all, what were brothers for? He and Will may have had their differences in the past but he loved his brother, he always has and he always will, and he knew his brother felt the same. They'd gone through the worst experiences together, growing up in a household devoid of love; the fear and uncertainty that came with his stint in the military but they powered through it; then through their dad's heart surgery that somehow ended up mending some of the old wounds from their childhood, not all, but it was a step in the right direction at least.

So objectively speaking, what was another hurdle to overcome? They were Halsteads, they broke noses first and asked questions later.

"Ready?" he asked as the nurses unlatched the breaks on the gurney.

"Not really," said Will under his breath.

Jay smiled a little, reaching out to grasp Will on the shoulder comfortingly. "I'm here, kay? So… just lean on me, I can handle it."

"Thanks, Jay," said Will as the gurney began moving out the treatment room; he could feel the concerned eyes of his colleagues following him all the way to the elevator but didn't look around. Instead he kept his eyes firmly on Jay following at his side, trying to take comfort in his younger brother's presence. "Thanks," he whispered under his breath as the doors of the elevator closed behind them.

It was a couple of hours sitting at Will's bedside as he slowly nodded off into much needed sleep before the first visitor stopped by. Dr. Rhodes who seemed to have come fresh from surgery stepped in, taking in the sight of the sleeping Will in the bed and immediately walking up to his side. Jay put down the outdated women's magazine he'd been reading, stretching out with a moan in the uncomfortable chair he was sure he'd be molded into before the end.

"How's he doing?" asked Connor as he stepped up, pocketing his stethoscope and crossing his arms over his chest.

Jay sighed, scrubbing his face with a hand. "Well, I'm no doctor but according to Nat it hasn't progressed completely but he was starting to feel some tingling in his fingers so they gave him something to help him relax."

"Christ," said Connor, shaking his head. "You come in to help people and this happens because of some tick someone brought over from Australia?"

"Yeah. It sucks doesn't it? I don't know if it's the Ranger in me talking, but I'd honestly take on a hail of gunfire rather than being brought down by a damn tick from across the globe. It couldn't have been a local one at that?"

Connor chuckled a little at that. "Will's strong through, he'll get past this in no time," he said.

Jay tried to force more optimism into his half-hearted 'yeah', but seeing his brother down like that, looking so vulnerable and young wasn't exactly inciting the most confidence in him; not that he didn't have all confidence in Will to kick it in the ass, but it was hard.

The sudden wailing of the machines all around caused Jay to jump slightly, his mind flashing back to a darker more terrifying point in his life before he came back down into reality just in time to feel the sensation of being pushed out of the way as Nat and various other medical personnel convened on Will. His eyes quickly glanced down to his brother, finding his eyes wide open and terrified, desperately gasping for air. He saw Will's hand reaching out for him and reached over without hesitation to grasp it tight.

"It's okay, Will," he said, pushing his way into the fray. He could feel the glare of the nurse on the back of his head, but Will needed him in that moment and he was damned if anyone was going to drag him away.

"J…ay," Will gasped through the air that he didn't seem to be able to inhale into his lungs.

"I'm here, Will. I'm here," he said, grasping onto Will's hand with both of his.

"'M… scared…" Will gasped, his eyes tearing up, his voice so soft that Jay had to lean in close to hear it.

Around him he could feel Will's bed being moved slightly to make room for Nat to squeeze in between Will's head and the wall behind her, the voice yelling out instructions and medicine doses that Jay couldn't even begin to comprehend, but he wasn't there for that. He was there for his brother.

"It's okay, Will, it's going to be okay," he repeated. "I'm here, alright? We're all here, so just… it's going to be okay."

Nat seemed to administer something to knock Will out because Jay felt his hand all of a sudden going lax in his grip before there was another hand on his shoulder pulling him back and away from Will. He was ready to start throwing punches but he turned around to find Connor's concerned face staring down at him.

"Give them room to work. He's going to be okay," he said, patting Jay on the shoulder a few times before relinquishing his grip. "It looks scary but this is all part of the illness. He'll be back on his annoying, redheaded feet before you know it."

Jay couldn't really find the humour in the situation but he appreciated Connor's reassurance. He couldn't tear his eyes away from the scene in front of him. "What's going on?" He asked without looking away, watching as Nat inserted a long see-through tube down Will's throat and feeling glad that he wasn't awake to experience it. He knew Will would have done his fair share of the procedure but it was a whole other ball game being on the receiving end instead. It probably felt the same being a doctor treating a friend and a colleague and watching them being put through treatments they were usually the one to perform because Connor didn't answer for a while and when Jay looked over at him he found his eyes on Will, looking as transfixed by the sight as he was. "Connor?" he called again, finally snapping the man out of his reverie.

"The uh… paralysis has progressed rapidly. He was intubated without the need for any additional paralytic which, while it isn't a usually very encouraging sign, is to be expected. It only means that the toxins has reached its peak incubation state and should already start working its way out of his system."

Jay could only nod robotically, taking in Connor's words but it was little comfort. He was looking at his brother that he loved and looked up to lying helpless in the ICU breathing through a tube. It was a difficult sight to behold.

He watched as the nurses hooked Will up to the ventilator and double checked the rest of the machines monitoring his vitals. His eyes quickly found Nat lingering by Will's side, reaching over to gently run her fingers through his hair; her glistening eyes staring at his face intently before she bent down to plant a kiss on his forehead.

Jay forced himself to look away from what should be a moment of privacy between them. He noticed Connor doing the same.

"Jay."

He heard Nat calling his name and finally looked back, seeing her beckoning him towards the bed. He hesitated for a moment before approaching. It was one thing watching from the distance at everything happening and the severity of Will's illness, but it was completely different looking at him from up close; finally taking in the paleness of his skin and dark circles under his eyes and the way he just looked so sick. The tube didn't help either, nor did the straps holding it place and covering part if Will's face from view.

"Hey." He looked up to find Nat's concerned eyes on him. "It's going to be okay, I promise."

"Yeah," he said. It was the only thing he could say. Subconsciously he reached to grasp Will's hand, feeling his skin cold and clammy in his grip; mindful of the crisscrossing lines covering what seemed to be every inch of Will's exposed skin. The uncertainty of everything was terrifying even to Jay who understood what genuine terror really felt like.

Thought just suddenly occurred to him causing him to mentally groan. "Damn it," he cursed under his breath. "Nat, could you uh, stay with him for a while?"

"Of course. What's wrong?"

Jay exhaled. "I should go tell my old man what happened. I doubt he'd even care but… you know… being a dutiful son and all."

"Sure, Jay. You go do what you need to do," said Nat before Connor stepped forward to interrupt them.

"Hey," he started, looking at Jay, "Why don't you stay? I can go pick up your dad."

"Really? I don't want to trouble you," said Jay though he was obviously more than happy to accept the offer.

"It's no trouble at all, man."

"You sure?"

"Yeah, of course," said Connor with a reassuring smile, stepping around the bed to grip him on the shoulder. "You just keep an eye on this guy for us," he said pointing towards the unconscious Will with a thumb, "I'll fill your dad in on the way so you don't have to stress about that at least."

"Thanks, Connor," said Jay, reciprocating the gesture. "I appreciate it."

Connor nodded and with one last look at Nat, turned around to leave the room, leaving the two of them standing on either side of Will's bed, gripping his hand tight in theirs. In the background only the sound of the steady beeping of the heart monitor and the gentle whooshing of the ventilator interrupted the heavy silence in the ICU room.

"Hey, Nat," he called, startling her out of the slight trance she seemed to have slipped into as her fingers continued stroking Will's hair, her eyes barely blinking from where they were trained on him. "Thanks," he said, "For taking such good care of him."

A small but appreciative smile broke onto her face at his words. "It's my pleasure."

They didn't anything more after that. Eventually Jay pulled the chair he'd been occupying closer to the bed, taking seat without releasing his tight hold on Will's hand and he just sat and waited, looking at Will's lax face for a sign of… anything really. Barely a couple of hours had passed since he last spoke with Will, since he last heard his voice and already it felt like an eternity. It was different than when he was in the army or when Will was off at med school leaving him alone to deal with their mom's sickness. Will was right in front of him and yet it felt like he was a million miles away. It was disconcerting and scary and Jay wasn't the type to get scared easily. But this was his brother, his family; he had very few of those left so he held onto the ones he had left with every fiber of his being and it didn't just apply to the family that he was related to by blood. It also applied to the family he'd found along the way; his brothers in the Rangers and his family at the CPD; he held them tight and he held them close and he'd do absolutely anything to keep them safe.

But he couldn't do anything to help Will and that was the most powerless he'd felt since he had to stand by and watch as his mother slowly withered away and died.

"You better not leave me, Will," he leaned in close to whisper into Will's ear. "Not you too."

Only the steady beeping and the hissing sound of the machine breathing for his brother answered him but he tried to take comfort in that. The sounds meant that at the very least his brother was still alive and in that moment, watching him looking so ill and just so… empty – it was really the only thing he could ask for.

Tbc.