Pasquale is an apprentice artist, working for Giovanni Rosso, but his life is turned upside down when Raphael comes to Florence as an emissary of the Pope. One of Raphael's entourage is killed and Pasquale ends up following alcoholic journalist Niccolo Machiavelli as he investigates. Then the mystery turns to a thriller, as Pasquale finds himself in possession of a valuable secret and is hunted across the city by agents of different political factions. The Spanish, envious of Florence's New World colonies, are threatening to attack, the Papacy is an uneasy ally, the fanatic followers of Savonarola are inciting the industrial proletariat to insurrection, and a black magician is up to something unsavoury...
McAuley avoids the biggest pitfall of alternative history, which is having the setting overcome the story. The background scenario is rapidly sketched in, with only a few passages of exposition, and only elaborated on as necessary. So the politics necessary for the plot is treated in moderate detail, but the world of the "artificers" — the industrialists and engineers behind the transformation of Florence into something akin to 19th century Britain — is barely touched on. This helps sustain suspension of disbelief.
The setting and characters are used to good effect and the story is well-paced and exciting, making Pasquale's Angel an effective and entertaining alternative history mystery thriller.