Major Clint Donovan followed his convictions and took a command in the Union cavalry but lost almost everything he held dearest. His parents and brother died, and his post-war plans to return to their ranch outside Independence, Texas, died with them. He and his wife started over on a homestead near Loyal Valley, and by December of 1869, they are quietly thriving. But thanks to a telegram from his former commander, Clint's about to find out that his family's "ill luck" was almost-perfect murder.
The mysterious Number Seven wants the whole of Texas for himself and will stop at nothing to get it. His wartime bid to take power in Independence failed because, of all the Donovans, Clint alone survived one of Number Seven's attacks. Now Number Seven's planning to cause enough chaos by killing Governor-elect E. J. Davis to seize the state before it can rejoin the Union.
Unaware of this history, Davis asks Clint to work with three military intelligence officers to stop the assassin Number Seven's men have hired. Clint agrees, and his wife and friends offer to help. But one of the intelligence officers witnessed the murder of Clint's brother, and he fears that if Clint goes to Austin himself, the assassin targeting Davis will recognize him. Can Clint's best friend, an engineer blinded by scarlet fever, find the solution in a failed experiment before disaster strikes the Donovans again?