Character Analysis
Vernet's the president of the Paris Branch of the Depository Bank of Zurich. Although he is largely driven by an innate sense of pride, loyalty, and propriety, the finer things in life do tempt him:
Despite his plush accommodations, he had always dreamed of owning a riverside apartment on L'Ile Saint'Louis, where he could rub shoulders with the true cognoscenti, rather than here, where he simply met the filthy rich. When I retire, Vernet told himself, I will fill my cellar with rare Bordeaux, adorn my salon with a Fragonard and perhaps a Boucher, and spend my days hunting for antique furniture and rare books in the Quartier Latin. (43.2)
Vernet and his powers of deception end up being crucial to Langdon and Sophie's escape from his bank, but because his loyalty ultimately lies with his old friend Saunière, he ends up betraying them. (He mistakenly thinks they're the ones who killed his good buddy.)
Don't worry, though, when he realizes that they were on Saunière's side the whole time, he comes clean to Fache and helps to clear up the whole messy situation.