side. >> lane then drew a diagram of the floor plan and charted the burn patterns using an arrow to point toward the heat source. >> examining this pattern indicates the direction of fire flow starting at the bottom of this pattern, where we first see charring, and then at the top of this where we see charring. if we drew a line across there, it gives us a direction from which the fire started. >> then he looked for visible signs of an accelerant, like gasoline, which makes a fire burn faster and hotter. >> when i pulled up the threshold, there was a slight odor, and that's why i cut it out and put it in a container. when i smell fuels that i've smelled for 40 years, i get excited because i believe they're there. but i don't allow myself to go to the point where i say it's