Arson investigator Doug Maple exits a building that is still smoldering. He approaches the squad who are just sitting around the rear deck of the truck. Walsh wiped some of the soot from his face and he took a drink from the bottle of water in his hand. Taylor was on the ground, her arms around her knees.

"Here comes Maple." She pointed out as she set her helmet on the ground and stood up.

"What's the word?" Walsh asked

Lt. Johnson was watching his crew shift around Maple.

"Well, looks like our arsonist is getting a little more familiar with the art of arson." Maple said

"Think it's the same guy?" Lt. Johnson asked

"Yeah." Maple replied, "Getting a little smarter though."

"What do you mean?" Walsh asked

"Well, each of the fires has had a back draft with it. The arsonist is using the back draft to hide the evidence." Maple said

"So in other words, our arsonist knows a lot about fire behavior." Taylor says

"Precisely." Maple replied, "We haven't seen the last of him, you can bet on that."

"If there is anything we can do to help your investigation." Lt. Johnson offered

"You've done all you need to, and that is your crews helping to preserve the evidence." Maple acknowledged

"Just out of curiosity." Walsh starts, "Are we the ONLY response area that this arsonist is targeting?"

Maple stopped for a moment and thought about it. In the 6 fires over the past 2 weeks that he had investigated- 3 of them were arson in the response area of the 55. The other three were unrelated arsons elsewhere in the city.

"This one, yes, only arsonist? No." Maple said as he walked back to his car.

Walsh looked around at everyone. They all felt the same sting from knowing that someone was after them. But who? Why? They could tell that they were in for a lot of sleepless nights until this arsonist finds his way behind the iron bars of a jail cell.

"I guess we can consider ourselves lucky that he hasn't struck any inhabited buildings." Lombardo said looking at the smoldering tenement that had been their last job.

"Yeah, but it seems like he is only after us." Taylor said

"Let's not worry about it. Let's just do our jobs and get on with it." Jimmy said

"Yeah, bad enough that DK got hurt in this mess." Walsh started, "We just need to double check and make sure that we aren't about to go into anymore back drafts."

"Yeah." Taylor agreed

Shortly after midnight, while the squad was all tucked up in their bunks to sleep, the alarm called out to them.

"Squad 55, Ladder 100 respond for alarm bells sounding. 11821 5th Ave."

Walsh sat up quickly and threw his boots on to go down to the truck. Taylor quickly raced behind him. Soon the bunks were empty, nothing but the ruffled sheets left behind.

They pulled up in front of the building to see the security guard standing out front.

"I have no clue why they're sounding." He said

"We'll check it out." Lt. Johnson replied

They were on the 8th floor. There was no smoke, so they were all just walking the hallway. Walsh moved the flashlight between doors as they checked them.

"Anything?" He asked

Taylor shook her head, "Nothing."

"Chalk this one up to an alarm malfunction." Jimmy said

"Yeah, let's go back to bed." Lombardo said

Lt. Johnson stopped in the middle of the hallway.

"What's up Lieu?" Walsh asked

"Something's not right." He said as everyone was silent.

Lt. Johnson looked at the ceiling and then back down the hallway they had just walked. He stood silently and listened.

There was a hissing sound followed by an explosion that blew the doors off of one of the offices they had just walked past. Everyone ducked for cover as the debris flew out into the hallway. Smoke immediately followed and they could see the orange glow.

"Get that standpipe pack hooked up." Lt. Johnson

Walsh rushed to the stairwell with the standpipe pack. He flaked the hose out on the landing and quickly removed the cap covering the pipe. Within seconds he had the hose attached and the line charged. Taylor took hold of it and she advanced on the flames with Walsh right behind her.

The fire rolled across the ceiling. Taylor acted quickly to stop the advance.

"It's moving too quickly, we need a second line in here." She said to Walsh

He grabbed his radio, "Lieu, we need to get a second line in here." He said

Lt. Johnson was in an office down the hall with Jimmy and Lombardo checking for extension.

"Lt. 55 to Ladder 100, get your crew to the 9th floor to search for extension. I need one crew with a second line to the 8th floor rear stairwell." He said

"On the way." Was the reply he got

Taylor and Walsh were trying to advance on the flames.

"This thing won't die!" Taylor said as the fire tried to quickly work its way around them

"Just don't let it get behind us." Walsh said as he looked around

"Where's that second line?" Taylor asked

"It's coming." Walsh replied

Part of the ceiling collapsed in front of them. They were forced to take cover for a moment.

"I think we could be in trouble." Taylor said

"Yeah, I am beginning to think you're right." Walsh replied, "We gotta back out."

Taylor agreed and they began backing away from the flames. Walsh turned to see the fire advancing to the rear of them.

"We've got a big problem." He said

Taylor turned, "Damn it! How the hell did that happen?"

The smoke and fire that they had been working hard to keep in front of them had worked its way behind them.

"Alright, now we gotta fix that." Walsh said as they quickly attempted to find the best way out.

They spin to attack the fire as the second line finally arrives.

"Took you long enough." Walsh cracked

Mac just shrugged his shoulders and opened up the nozzle.

"What can I say?" He asked

Together they worked on putting out the fire.

Lt. Johnson, Jimmy, and Lombardo were still searching the adjoining offices for extension. Lt. Johnson looked at the bottom of all of the doorways.

Lombardo prepared to open the door when his superior stopped him.

"Joe, don't." He said as he approached and felt the door

Lombardo watched as did Jimmy.

"The door's hot, but there's no smoke coming out from under it." Lt. Johnson said

"Back draft." Jimmy said in reply

"Precisely." Lt. Johnson said.

They would have to let the fire starve itself before they could open that door. It was too dangerous to open it now; they could end up like DK with broken ribs and a broken collarbone or worse, they could end up dead.

Lt. Johnson watched over the rest of the operation very carefully. He was right; the room did burn itself out. They finished up the firefighting and waited on Doug Maple to do his investigation.

They rested on the steps outside of the building. Taylor rested her elbow on her knee. She was propping her head up with her hand. They were all tired. Walsh was resting against Taylor. Lombardo was resting against the railing and Jimmy was sitting behind him.

Maple exited the building.

"Well you are definitely keeping me busy." He said as he looked around at the exhausted squad. "You're lucky that you let the back draft snuff itself out. Had you opened those doors we'd probably be making arrangements for 3 funerals."

"Fortunately, that was prevented." Lt. Johnson said

"Fortunately, it preserved evidence." Maple smiled, "The guy only wanted me to think he was an amateur. From the evidence I gathered, he's a pro. But, I've never dealt with him before now."

"Any idea on who it could be?" Walsh asked

"Not yet, but I have a few thoughts on it." Maple replied, "You guys try to get some sleep. I will keep you posted."

Lt. Johnson looked at his tired crew.

"Alright, let's go home."