The Cryptographer (Second Sons Book 1)

Everybody has a secret, but some are harder to decipher…
England, 1813. Aster Tanner is alone in the world and keeps a roof over her head by working the one asset she has – her mind. She needs her job; she does not need a Scotsman underfoot, making her heart flutter with heated glances and impertinent questions.
Iain McIntyre, Captain in the Second Dragoons, has a confidential assignment: find a list rumoured to name traitors working against England. He is looking for anything unusual — like a woman working as a secretary. He tells himself his fascination with the lass is because she holds a man's position, and nothing to do with his rising desire to know the sharp mind hidden behind her darkened glasses.
When Aster is targeted by those intent on recovering the list, she must decide who to trust. She has seven encrypted names. But whose? Meanwhile, Iain is on the trail of a double agent. Time is running out, and secrets must be decoded before lives and hearts are sacrificed.