This was BRP Call of Cthulhu, in the 1920-1930 era.
Colonel McPherson was a retired officer with a love for explosives... Any time he would have to investigate on the Mythos, he would bring some dynamite with him.
One day, McPherson and his colleague intruded into a vampire's lair. At some point, as they were scared they decided to burn the house. So, they doused alcohol in some rooms and set it afire. McPherson was so used to have dynamite in his pockets at all time, that he forgot he had some on him, and that it might be dangerous.
Anyway, as the fire began raging and the PCs considered which way to take to escape the place, the vampire appeared. As the odious foe jumped on McPherson's colleague, the colonel immediately doused the vampire with more alcohol. Angered, the now burning vampire released its first victim and turned on McPherson instead.
As the retired colonel was wrestling with a flaming vampire, the dynamite in his pockets eventually caught fire.
All that remained of the vampire's house was a big crater.