Hin stayed most of the time with Howl's friends, running from Madame Suliman. None of them were sure if he was a spy or a friend, and nor am I sure about that.
Was Hin a prisoner or a spy?
Hin stayed most of the time with Howl's friends, running from Madame Suliman. None of them were sure if he was a spy or a friend, and nor am I sure about that.
Was Hin a prisoner or a spy?
Hin (or Heen as written by the US localization) is Madame Sulliman's dog.
We know this because Sulliman tells Sophie this directly.
Sophie: That's not your dog, is it?
Sulliman: His name is Heen. He's my errand dog,
It would appear then Hin is initially working for Sulliman.
When Sophie and Howl make their getaway, Hin joins Sophie to live in the castle as a normal everyday dog with everyday day struggles. At the end, we see Sulliman communicating with Hin through her crystal ball who questions his prolonged absence: "why didn't you report in earlier?". She also calls Hin a "traitor".
We can surmise that Sulliman sent Hin to be a spy but that Hin abandoned his post after being swayed by Sophie's conviction.
Spy and prisoner both imply obedience but I wouldn't characterize his betrayal as disloyalty. Rather, I would say that Hin is a free agent and exhibits compassion. Coupled with his humility, Hin is quite an admirable dog.