Feed the Crow — Tony Masero

His military commander orders Captain John Page and his Portuguese translator Adelino, on a vital mission of political importance. The Peninsula War of 1812 rages around them and their way is fraught with danger; it is a mysterious path that leads them down into the depraved sexual underworld of Lisbon high society, where they discover a devious predator is on the loose, a murderous killer who takes shocking mementoes from the victims.
Page finds romance and peril as he braves the bloody fields of Badajoz and Salamanca in search of his prey. But the deadly trail does not end there; he must suffer both loss and hardship and cross war-torn Europe before he can come to grips with the evil force that threatens everything he owns.