Without the benefit of my own vehicle after taking a taxi to the lab the previous night, I was stuck with public transportation once again and, due to that fact as well as my lack of sleep, I found myself quite irritable with Special Agent Jake Parker by the time I pulled up outside his building. I hardly even glanced around as I made my way through the lobby and to the elevator, punching in the button for the eighth floor once I double checked the text from Dr. Warner.

I made my way down the carpeted hall to apartment 803 and knocked on the door, glancing down at my phone at a text from Kacey. My fingers were busy typing away a response when the door swung open.

"What gives, Parker? We're late and you haven't answered any of my-"

Finally I'd looked up to see that, standing in front of me, was absolutely not Special Agent Jake Parker. Instead, it was a five foot nine skinny blonde wearing only a white dress shirt unbuttoned just enough for her black lace bra to peek through the top. Classy. I couldn't help but smile before I managed to bite my lip and recover.

"Oh, I'm so sorry," I said, keeping my amusement at bay as best as I could. "I guess I know why he wasn't answering my calls now. I'm Dr. Madeline McKinnon."

"Tiffany," she replied in greeting, sticking out a hand. I shook it, biting my lip. Suddenly, Parker slid into the room behind her as if he'd come running at full speed when he'd heard my voice. He was clearly fresh from the shower, hair still damp and feet bare as he quickly buckled up those black suit pants I'd become accustomed to. I only had a moment to enjoy the fact that I'd been correct on my evaluation of his physique as being something he worked quite hard on before I was enjoying something else altogether; seeing Special Agent Jake Parker flustered for the first time.

"Doc," he spat in surprise, looking from his amused partner to the half naked woman in his apartment and back again. "What- um, what are you doing here?"

"It's ten o' clock, Parker," I answered, suppressing a laugh as he grabbed a white tee shirt and quickly pulled it on.

"Oh, uh, right. Yeah. It is," he said, running a hand through his hair and glancing at the clock. "Look, Tina, I have to get to work so-"

"Oh, of course!" she squealed, throwing her arms around him and kissing him on the cheek. He turned bright scarlet as his eyes met mine and I thought my face might crack from my own smile. "I should get to work too actually. They'll be missing me soon enough, I'm sure."

"Oh, what do you do for work, Tiffany?" I asked, putting emphasis on her name as he'd just gotten it wrong. I watched him close his eyes as she went to gather her things.

"I'm a school nurse," she explained, pulling off the shirt and getting dressed right there in front of us like the person with the least amount of shame in the world. Though, she didn't have any reason to be ashamed. "So it's no biggie if I'm late sometimes so long as we haven't had a rush of kids coming in coughing or anything."

"Coughing," I repeated quietly, the smile vanishing from my face as I was struck by a realization. Parker raised a brow but Tiffany was back on him again, kissing him on the other cheek as she pulled her coat on and grabbed her bag.

"Okay, I'll see you later?" she asked, heading past me toward the door. "You'll call?"

"Yeah," he nodded, following her to the door and shutting it behind her after a few more moments of mushy goodbyes from the bouncy school nurse. When we were alone, he turned back to me with a sigh. "Listen, I can explain. I didn't-"

"Coughing," I repeated louder, looking up at him as if I expected him to get it.

"Yeah, you said that," he told me with a frown and a creased brow. "I don't know what it means."

"We need to get to the Lucas house," I told him, pulling out my phone, my fingers already dialing the number as I headed for the door. "Can you drive?"

"Yeah, but why are we-"

I wasn't listening. Someone had already answered on the other end of the line and I was talking to them now.

"Mr. Emerson," I said into the speaker as Parker grabbed his shirt, tie, and suit jacket and we headed to the car, him getting dressed the rest of the way in the elevator as we waited. "Can you pull up the atmospheric radar for Sunday night?"

"Sure," he answered and I heard some shuffling. "I'm going to put you on speaker so that I can run the radar on the monitor. Dr. Warner is here."

"That's fine."

"Location?"

"Benning," I told him and Parker looked my way. We had made it to the street and I put the phone on speaker as we approached the SUV and hopped inside as quickly as we could.

We all waited quietly while Mr. Emerson typed into the tablet.

"Rain," Mr. Emerson said a moment later. "Heavy rain."

"Rat poison," I thought out loud.

"Doc, what's going on?" Parker asked.

"The mother. When she got all upset and kicked us out, she was coughing," I told him.

"Yeah, so? Must be something going around. What of it?"

"No," I shook my head. "Not a virus. A gas. A toxic gas."

"Oh my..." Dr. Warner gasped from the phone and I found myself nodding, pleased that someone was finally understanding. "Phosphine."

"Precisely," I said.

"Oh," Mr. Emerson added. "Wow."

"Would someone like to clue in the dumb guy on what's going on here?" Parker snapped, frustrated.

"Zinc phosphide is a common chemical in most rat poisons," I explained. "Harmful only if digested in pellet form. But if it were to be combined with dihydrogen monoxide-"

"If it got wet," Dr. Warner explained more succinctly.

"Yes, if it got wet," I continued, "it would turn to phosphide gas. A highly toxic gas known to cause fluid buildup in the lungs within hours of exposure."

Parker's jaw dropped in understanding.

"If Chelsea Lucas were being held somewhere damp... somewhere with a case of rat poison nearby..."

"Like a basement," my partner finished for me.

Parker's eyes met mine with a look full of meaning and he reached down to flip on the sirens. I said a hasty goodbye to Dr. Warner and Mr. Emerson as Parker called it in and pressed down on the accelerator.

"Let's hope Mrs. Lucas didn't take your implication seriously," Parker said as he whipped the car to the right and I grabbed the handle above my head to steady myself.

"Even if she did, I highly doubt she would be able to reason out the cause of death for herself," I shouted to be heard over the siren. "She doesn't strike me as a woman interested in the sciences. If she did tie her daughter up in the basement, she likely thinks Chelsea died of shock or neglect. She thinks she killed her. If not purposely, at least symbolically. Her disposal of the body shows a feeling of guilt."

"But wet rat poison. I mean, no one knows about this gas stuff. It was an accident."

"An entirely avoidable accident. Mrs. Lucas has remained in that house, likely still with the wet poison, and the only symptoms she seems to be exhibiting are a slight cough. Chelsea would have had the same, perhaps even less given her much younger more robust immune system, if her mother hadn't locked her in an airtight basement with a toxic gas."

"Still, she didn't intend to kill her."

"But she did intend to tie her up like an animal."

"Doc-"

"Oh, turn here!"

He yanked the wheel to the side and I slid halfway off my seat. Before I could fall, though, Parker's arm shot out and gripped my waist, holding me securely against the seat. I looked down at his arm and then up a him through my disheveled hair.

"You okay?" He asked when our eyes met.

I could only nod.

"We're here," he said and whipped the car up to the curb and threw it in park.

We leapt out of the vehicle and nearly ran up the front steps, pounding on the door. No one answered. We looked at one another once before Parker pulled out his gun. He nodded at me and I did the same, pulling mine from my hip. I had a momentary sensation of anxiety as I realized I had never drawn a weapon outside of a warzone before and especially not on the porch of a run down house in a residential neighborhood but I kept my focus as Parker warned the inhabitants of our arrival.

"Mrs. Lucas," Parker called out. "Special Agent Jake Parker, FBI. I need you to come out of the house with your hands up."

We waited. Nothing happened.

"Mrs. Lucas, now!"

Again nothing.

"She could be poisoned," I told him.

At that, Parker nudged me aside and brought his foot back before kicking hard against the door. The screen bowed and shattered at the force and a feminine scream sounded from inside. We entered the house, guns drawn, and saw Mrs. Lucas sitting on the couch, shaking, tears streaming down her red face.

"Shoot me," she squealed. "Chelsea's gone! Just shoot me! I've got nothing else to live for!"

"Mrs. Lucas," Parker said, putting his gun away as he approached the woman. I kept mine drawn in case my partner needed assistance but he didn't. He helped her gently to her feet before turning her around and securing the handcuffs around her wrist. "You're under arrest for the murder of Chelsea Lucas. Anything you say can and will be held against you in a court of law. You have the right to an attorney. If you cannot afford one, one will be provided to you..."

As Parker mirandized the grieving mother, I lowered my gun. I heard other sirens approaching from outside the window and watched as Parker marched Mrs. Lucas out to meet them. I let him go, remaining in the house myself. Knowing there was no one else inside, I turned to face the hallway and made my way slowly down it, keeping an eye out for any doors that might lead to the basement. I found it on the opposite side of the kitchen and nudged it open. There were stairs leading down into darkness. Pulling my phone from my pocket, I turned on the flashlight and made my way slowly down them.

I emerged into a small room, maybe only the size of a large closet or a prison cell. It was damp, that was certain, but it wasn't anywhere near large enough to restrain a teenage girl. Shelves littered every wall, making the available space even smaller. They were filled with canned food, preserved fruits and vegetables, but no rat poison.

"Doc?" Parker called from the top of the stairs.

"Yeah," I answered. "Down here."

I heard him descending the stairs a moment later.

"Kind of creepy down here, isn't it?" He asked when he reached me.

"This doesn't make any sense," I said, thinking aloud. "She couldn't have tied Chelsea up down here. There's no room. And there's no rat poison."

He frowned as we both slid the lights from our flashlights around the room.

"Well, we'll take her in anyway," he said. "Maybe she'll confess."

"Wait," I interrupted. The light from my phone had just caught on something metallic behind a jar of green beans preserved on the far shelf. I approached for examination. "Help me move this shelf."

Parker didn't ask any questions. He only grabbed the shelf and pulled back. I pressed my shoulder against it to help as much as I could. When it was sufficiently out of the way, I shined my flashlight into the space it had left behind to reveal the small door hidden there. We glanced at each other before I took a step forward and unclasped the lock.

I pushed it open and we stepped into a much darker and much larger room, likely the original basement. We entered with our lights, straining to see what was down here. Parker went to the left, I went right.

"Rope," he said after a minute. "Frayed like she tried to cut it from the wall but still here. I guess she was pretty confident we wouldn't find this place."

I looked over at the cord he was pointing to and nodded as he took out an evidence bag and a pair of gloves and began to collect it.

Meanwhile, I found a pile of typical household materials. Bags of mulch, potting soil, a few cinder blocks and- "Parker."

He looked over to see me pointing to a bag of rat poison. An industrial sized value bag with a giant cartoon rat with X's for the eyes imprinted upon it. And on the wall beside it? Clear water damage.

"We should get out of here," I told him. "The gas."

"Yeah," he agreed, still staring at the bag. "Let's go."

Covering our mouths as best we could, we made our way out of the secret basement and back upstairs to a much busier scene. The crime scene unit had arrived and Miss Daniels was directing the collection of evidence from the kitchen. I saw one of her techs bagging the much smaller bag of rat poison I'd noticed on my first visit. Others were examining anything in the home that appeared it might be used to bind.

"The basement," Parker told her as we approached. "It's all in the basement. But wear a mask."

She nodded in understanding and called to some techs to head to the basement. Parker led me toward the door and out to the SUV. We said nothing on the walk to the car. I was taking deep breaths of fresh air, trying my hardest not to think about how terrifying Chelsea Lucas' final struggles to breathe must have been, bound and chained to the wall of her own basement.

It was a strange, disconnected feeling leaving that house. We had solved the case. We had found the evidence. But it had done nothing to diminish the horror of a teenage girl's last moments. Still, it was over. Wasn't it?

"Now what?" I asked before I really thought about the question.

He frowned as he held open my door and said, "Now, we get that confession."