Well Act I I'm kinda hazy on, and Act II should be pretty obvious.
Act III:
The Boy is called on to fight in World War I, and he's sent to the front lines. Before going up he meets the Poison Woman, who as her name suggests is a dealer in all sorts of deadly substances. As he's fighting the war, he comes across the Mustard Gas Brigade or some shit like that, and they nearly kill him as they pummel his entire squad with grenades and toxic substances and whatnot.
The Boy is on the edge of death, no help for him now....until suddenly someone grabs him and deserts the battlefield with him. They return to wherever the Boy is from, and he learns there that his rescuer is his father. His father tells him the story of how he met Ms. Terri and essentially of his conception.
This is where it starts to get a little hazy for me, but apparently the Boy's father had another son, a legitimate half-brother to the Boy. The father comments how much the Boy looks like his half-brother. For some reason that I'm not sure of yet (my theory is vengeance for the hell he'd had to deal with as a bastard son), he finds and kills his half-brother, and proceeds to masquerade as him (as said, "You look just like him"). That's the best I've got.