Jacque Henri is an expert French assassin, whom Richard Castle hired to help him rescue Alexis Castle, when she was kidnapped and brought to Paris. He agreed to help Castle rescue Alexis and began aiding Richard Castle, and after getting information from an accomplice of his Le Taupe, who specializes in technical equipment, he proceeds to aid Richard Castle. Eventually finding the place where Alexis was being held, Henri discovers a surveillance bug and through it was able to strike a deal with the kidnappers to release Alexis.