After the betrayal at Isstvan, Horus begins his campaign against the Emperor, a galaxy-wide war that can lead only to Terra. But the road to the final confrontation between father and son is a long one – seven years filled with secrecy and silence, plans and foundations being formed across distant stars. An unknown history is about to be unveiled as light is shed on the darkest years of the Horus Heresy, and revelations will surface that will shake the Imperium to its very foundation...