No fire

Driving home (truck running like always), stopped at store, came back out and truck would not start. Towed it home
Figured out I was not getting fire. Tested cylinders one and two.
Changed out Ignition coil, distributor cap, and rotor button.
Plugs are a little dark, just put them in about six months ago and wires look good. They were changed about eighteen months ago. Checked all fuses and none were blown.
What should I be checking next to find out why no fire?
I am at a loss of what to do. Help!