The call went over the radio at just after 12:30 a.m., when Jo Danville had been certain her week was finally over. It had even ended on a high note, Friday rolling into the wee hours of Saturday as she laughed over a story Mac had shared about the first time he drank a beer in front of his father. It had been one of their late dinners, one of those nights when she'd charmed him out of the lab knowing that if she didn't, he'd work till morning and barely notice.

There were more and more of those nights shared between them lately, but she still wasn't sure if Mac was saying yes because he wanted the company or because, like her, he felt that heady mix of attraction, fear, and affection that were making her more certain every day she was falling in love.

Sometimes she was sure he felt it; and other times, when he'd pass up a chance to take her hand or make eye contact, Jo wondered if what he felt was the inevitability of having to give her the "just friends" speech.

Tonight when she'd said good-bye to him, there had been this moment when it seemed like one of them might finally take that last little step to either start things or end them... but then Mac's cell phone had rung, and the spell had broken, and Jo had walked away with a wave as he answered.

She knew her weekend free to soak in the tub, sleep in, and have time for both a massage and yoga-courtesy of Ellie's friend Brianna who had invited her for the whole President's Day weekend-would be spent replaying that moment, musing over the "what ifs" and "what might still be possibles," which should've made her feel like a first-rate loser, but really just made her feel more hopeful than anything unrelated to her children had in years.

But the self-indulgence would have to wait until after one more work-related delay. A fire in a warehouse near NYU that was notorious for college parties had left the fire department with an arson investigation and a half-dozen bodies at least. Jo had no doubt that Mac Taylor was en route to the scene himself, his promise to go home and get some sleep forgotten in his never ending quest to try and right every wrong he came across.

It drove her nuts that he ran himself so ragged, and yet it was one of the things that she adored about him, too. That need for there to be closure, for someone to truly be brought to justice... it pushed him to his limits, often beyond them, and yet it was what made Mac Taylor who he was, and it sometimes left her in awe of him.

Not that she'd ever tell him that. Jo knew that she was the only one in the lab who had the seniority on the job and off to try to counter the workaholic in Mac, to point out the need for basics like food, sleep, and an occasional attempt at a real life.

The crime scene was already active and crowded as she pulled up, surveying the large number of fire trucks still on site, the ambulances that remained treating the less wounded survivors, and the black-and-whites that were already busy working crowd control. Jo grabbed her kit, locked the car, and shoved her keys in her pocket before she began pulling a set of gloves on as she approached the still smoldering warehouse.

"Ma'am, this front half of the building's been cleared for your team," the fire captain informed her. "We're still working on some hazard clearance in the rear."

"Any idea how many people made it out?"

"Rough estimate is thirty. Six transported to the hospital, the rest banged up with everything from smoke inhalation to minor burns."

"How many fatalities?" she asked.

"At least three up here. They think four in the back, but it's still hard to say. Both of the main exits were blocked initially. Some kind of wooden barricades that partially burned in the fire themselves. Most of the kids who made it got out the side windows."

She nodded and headed inside, stepping carefully not just for safety, but to make sure she wasn't trampling over any key evidence. Setting her kit down, she pulled out a camera and began by taking photographs, archiving everything about the victims and where and how they lay before they were touched. She was just getting started when a familiar gravely voice called out to her.

"So is it my turn to lecture you on going home?"

Despite the gruesome scene, Jo caught Mac smiling at her for just a moment before the horror that had happened a few hours earlier caused his face to fall.

"Blocked doors, accelerant-someone wanted to cause a lot of death here tonight."

"Thank God someone got those windows pushed out, or we'd have a lot more fatalities," she stated simply, a slight shudder running through her.

"Since we can't go to the back yet, I'll start scouting trace while you finish the photos."

Jo nodded her agreement to Mac's plan and returned to the task at hand. After documenting the position and surroundings of the victim near the front door, she moved to the two victims who were lying together near the windows that so many others had escaped from. The victim on the bottom was female, obvious from her still partially intact high heels and the long hairs that had burned and scattered around her head. The second victim appeared to be male, and from his position, it looked as if he'd been trying to shield the female from something, likely either the fire or the desperate partygoers trying to escape.

It wasn't until she moved in to get closer shots for possible identification purposes, in case the bodies held no I.D.s, that she saw it... the gold butterfly charm bracelet on the left wrist of the female victim-charred and twisted, but still recognizable.

Jo had helped picked that bracelet out when Tyler told her that he "couldn't go to Natalie's birthday party empty-handed."

Her mind went into protection mode immediately, pushing away the unthinkable. This was New York City, and they'd gotten the bracelet at a big department store. It was hardly one of a kind, and it was popular with college girls-the sales lady had told them so. And what were the chances? What were the awful chances that she'd walk into a crime scene and...

She set the camera down and moved to the male body. When she'd heard the radio call, Jo had almost texted him, just to reassure herself that he was somewhere else-anywhere else-than at the ill-fated party. After all, Tyler's apartment was in the East Village, too. It wasn't impossible. But then she'd imagined him laughing at her for being overprotective, teasing her for months about how she loved that modern technology allowed her to mother him no matter where he was.

Her gloved hands traced lightly over the body, looking for something to put her mind at ease while she tried to stay cognizant of her responsibilities as a CSI. Tyler was a legal adult now, a grown man old enough to vote; she didn't know half of what he did when he wasn't in school. He could be anywhere, and the truth was, overprotective mother bear or no, there was a limit to the access he gave her.

Her hand stopped as she touched something that could be a wallet. It was charred, burned into a heap of fabric and skin melted together, but she managed to pry the two sides apart, to see the charred remnants of the New York State driver's license that lay inside.

"Jo?"

The breath left her body, and even though she heard Mac call her name, she couldn't respond, couldn't even turn to see him. Her eyes could only shift from the horrible bit of proof in her hand to the body that lay just in front of her, face down, arm still resting over the person he had so wanted to protect, a sweet girl named Natalie who he'd met in Chemistry lab and couldn't stop talking about.

"Jo? What is it?"

She couldn't breathe. She couldn't force her body to take in air, and she couldn't stop her eyes from shifting back and forth. Was she hoping that something would be different the next time, that another name or face would be on the melted I.D. and end the nightmare?

"Jo!"

His hands were on her now, and Mac turned her toward him, roughly, his concern getting the better of him. She saw him then as he tore her away from the body just enough that it made her eyes shift, but she still couldn't breathe, still couldn't find any air, and her body began to shake in his hold.

"Jo, you have to breathe. Jo, breathe!"

He shook her, and when it didn't work, he shook her again. And when that still got no response from her body, as the edges of her world began to darken and fade from the deprivation of oxygen, she felt his arms wrap around her body.

"You have to breathe. Damn it, Jo, breathe!"

He jerked her up as he brought them both to their feet, and the movement was enough to break her body's paralysis and her throat burned as she choked in air. Her left hand gripped his shirt as Mac lowered them back down and set her away from him just enough so he could see her face.

"What happened? What is it?"

Her right hand still held the awful evidence, but as he asked, as her brain tried to process the words to answer, it fell free and smacked against the floor. Mac held her steady against him as he reached down and picked it up with one hand, his fingers working the bitter remnant open.

Jo watched his face, praying something there would tell her she was having a delusion, that some awful sickness had overtaken her and this vision was the result. But tears pooled in his eyes the moment he took in the contents of the once pristine Italian leather wallet that she had given her son as a congratulations gift for getting into NYU.

"Oh, my God. Oh, Jo."

Her hand gripped his shirt tighter as Mac pulled her against him, his other arm wrapping back around her. She heard another voice, felt the vibration in Mac's chest as he responded to whoever else had come, and then she felt her body leave the ground as he lifted her up and moved her away from the terrible place where her world had imploded.

"I need one of those buses now!"

Mac realized he was screaming as if she'd been shot, as if blood was flowing out and stealing her life away, but this felt worse than that, and he knew she was in shock. Any doubt he'd had after the breathing incident was erased when she had no reaction to him picking her up and carrying her away from the body... from Tyler. He'd half expected her to fight him, to refuse to leave her son even though she was powerless to help him. But Jo had done no fighting, offered no refusal. Instead she lay slack against him, cradled against his chest, and as broken as he'd ever seen a human being in his life.

As the paramedics moved one of the ambulances closer to the scene, patrol officers leading them through, Mac saw Flack and Hawkes jump out of their just parked vehicle and race toward them.

"Mac, what happened?" Sheldon asked, immediately shifting into doctor mode.

"Shock. I... she couldn't breathe, and now she can't get a normal respiration."

He stopped where they were and laid Jo on the ground, her had in his lap as Sheldon began to check her over. The paramedics joined them a beat later, bringing a gurney, and soon they were moving her to the open ambulance doors, Sheldon climbing inside, barking out orders that the medics followed methodically.

"Mac, what... what the hell happened?"

Don's hand fell on his shoulder, and as Mac looked up at his friend, he felt a wave of stress crash into him. He had no idea how much time had passed since he'd noticed Jo staring so intently at something she held out of his sight. It was probably no more than a minute, maybe two. But that was all it had taken for him to realize that everything had changed, not just for Jo, but all the people who cared for her, who would have to live through this pain with her.

"Tyler..." he said, his voice breaking with the effort to give voice to the unfathomable. "Tyler's inside. Jo found his body."

"That's..." Don stumbled back, stunned. "No, that's... that's impossible. It has to be a mistake."

Mac looked at him and shook his head.

"I saw the I.D. I... I wish to God it were a mistake, Don, but... you didn't see her face. It's him."

He had ordered a patrol officer who'd come over to see if they needed help to stand watch over the bodies by the window, to make sure no one else came near them, and though everything in Mac wanted to walk to that ambulance, he knew that he had to go and finish the work Jo had started so that the identification was definite.

"Lindsay and Danny are on the way?"

Don nodded, and Mac motioned with his head toward the vehicle that now held Jo out of his view.

"Tell Hawkes to stay with her. I... I need to go back in there."

Flack turned his eyes to the burned out building and let out a long, slow breath.

"How in God's name did this happen?"

And this time Mac was the one with the comforting hand for his friend's shoulder.

"We'll find out, Don. We'll find out."

Flack nodded and then turned toward the ambulance, and as he stepped away, Mac willed himself to walk back inside the warehouse.

Danny and Lindsay arrived minutes later, their faces as they joined him inside telling Mac that they knew the awful news. Together, they finished the photographs, collected trace, and Mac assembled DNA samples from each victim so that Sid could confirm the identities of their victims before any other parents had their worlds torn apart.

The back area of the warehouse was finally cleared, and the team repeated their work there, the total number of fatalities rising to eight as they found five more bodies. Six of the victims had tentative identifications of some sort-driver's licenses or school I.D.s found on the bodies-but the others would require dental or DNA matches. Mac's stomach knotted at the idea of all the heartbreak this one night would cause.

"Mac."

Sheldon's arrival surprised him, and he stood, placing the last DNA packet in his kit.

"Is she alone?"

"Flack's with her, and the paramedics. She came around and her vitals are stable. And she won't let them transport her. She wants to talk to you."

Leaning down, Mac closed his kit and stood, the weight of it almost toppling him. Three hands reached out to steady him, and he gratefully looked at each of his colleagues... at his family.

"We'll finish up here," Danny said. "And you tell Jo we'll, uh... we'll ride back with Tyler ourselves."

"Yeah," Hawkes added, "We'll make sure that Sid and our team are the only ones who go near him."

Lindsay's hand touched down on Mac's arm then, and he looked toward her.

"And tell her we're here, anything she needs."

Mac smiled slightly, touched as always by the strength these people showed in the face of tragedy, even when it had devastated them.

"She knows that, but I'll tell her anyway. Thank you all."

She was sitting on the back ledge of the ambulance, a blanket wrapped around her shoulders. As he neared, Flack stood up from where he sat beside her and came forward.

"I've got every man I could find canvassing. I'll start pulling info on the vics as soon as you're clear to..."

He looked back over his shoulder at Jo for a moment before his eyes returned to Mac's.

"I don't know how she's still functioning. She called some friends of hers at the FBI to have them get ahold of Russ. He's in California on an assignment. I'm not sure I could've made that phone call."

Mac nodded and took a step toward the ambulance.

"I've got her. You go do what you need to do."

Flack promised to call as soon as he had useful information and walked into the crime scene. Mac moved to the detective's former position at Jo's side. He couldn't bring himself to ask how she was, so he simply sat his case down and then reached out and took her hand.

"They promised to have someone tell Russ in person. I just... I can't tell him this over the phone."

"It's good he'll have someone with him," Mac answered, and Jo nodded.

"And I called Brianna's mom. The girls were still up playing video games, but I just... I didn't want to drag her home in the middle of the night to tell her that her brother is... So, um, Sarah-Brianna's mom-she said she'd pull the cable so they didn't see anything online, and she's gonna bring Ellie back first thing in the morning."

She stood suddenly, catching him off guard, and Mac instinctively reached out to keep her close, her earlier physical collapse still too recent and real for him to not be concerned.

"This is a terrible thing for me to ask. I shouldn't even ask it, but..."

Jo pulled her hand away from his so both her palms could press against her face. Mac stood and moved closer to her, his fingers gently peeling hers away so that her eyes came back into view.

"You can ask me anything, Jo."

She took a deep breath, the exhale shaky and uneven.

"Will you be there when I tell her? I just... I'm not sure I can do it alone."

He knew that wasn't true. He knew she could. But the idea of her having to tore at his heart, and Mac used his grip on her hands to pull her into him, his arms looping around her.

"I'm here, Jo. I'll be here, whatever you need, okay?"

He felt her hands take hold of his shirt, twisting the material as she had earlier in the warehouse. Then he felt dampness spread through the fabric as she pressed her face into his chest and a sob tore free from her throat. The sound drew moisture from his own eyes, and Mac let his lids fall closed as he nuzzled the top of her head and prayed for the strength that he would need to see her through what was to come.