In the Pilot, Dean drove away after dropping Sam off at home and then a few seconds later burst in to save Sam from the fire. How did Dean know Sam and Jess were in trouble?

link
watch it and you'll understand :))

I think and I dont know if this is right or not but Dean turned around and came back and when he heard Sam yelling he came in to help him

he Knows coz hes seen it happen before with his mum! he knows the signs and he saw them 2 wen he drove off! he also had a feeling it would happen to sam!

.'cause Eric told him:P
Just kidding.
Dean was not happy with Sam not going with him to find John, then he returned to Sam's home,was when he heard Sam screaming and took him away from there.